Applying Bayes&#39; Theorem to law and forensic evidence I realise that every scenario is unique, but are there are guiding principles forensics investigators use to estimate the prior probability of guilt of a person (P(G)) when using Bayes' Theorem to estimate the probability of guilt after taking evidence into account? Are there any widely accepted resources that list the hit rate (P(E|G)) and false alarm rate (P(E|I)) for different types of evidence?
You have to deconstruct the question on a country by country basis. In the US legal system, the question presupposes something incorrect, that there are &quot;investigators&quot; who play a rule in legal system, and their job is to determine guilt vs. innocence. That is something determined by the &quot;finder of fact&quot;, typically the jury (it could be a judge, when you have a bench trial). The finder of fact may take into consideration testimony provided by a witness, and it is possible that a witness is an expert in some relevant area, who might attest to the significance of a claimed piece of evidence. The expert cannot testify on the question of guilt. For example, a DNA sample might be admitted as evidence that the defendant was present in certain circumstances, which could reasonably lead the finders of fact to conclude that the defendant did strike the victim. A DNA sample cannot testify, therefore some expert must testify about the significance of the sample, specifically whether the sample &quot;might have&quot; come from the defendant, or &quot;definitely came from&quot; the defendant. Others will testify as to the circumstances surrounding the collection of the sample. It is then up to the finder of fact to evaluate all of the evidence plus understand the instructions regarding the criteria for finding the defendant &quot;guilty&quot;. Theoretically, Bayes Law could enter into an expert witness's (scientific) testimony, and likewise an opposing witness could contradict the putative relevance of BL in terms of reaching a scientific conclusion. BL could enter into the discussion at the level of the bottom line &quot;definitely/possibly does come from the defendent&quot;. The only practical way that I can see BL entering into the courtroom at least non-gratuitously would be if there is a dispute over the reliability of a certain test, thus should the testimony be allowed in the first place (it might be excluded as being unreliable). There is a genre of research (for example this) that addresses the problem of sketchy statistic inferences, pointing to a role for BL. I would say that the prospects are dim, not bright.
There are all manner of reasons that evidence can be excluded at a trial, most of which are set forth in rules of evidence. If the evidence was not admitted on the grounds of relevance and the charge was speeding, I presume that the reason that it was found not be to relevant was that it was not possible from a video to determine how fast someone was driving and there was no dispute in the case over who was driving. If the defendant could have articulated some reason that the video was relevant to those points, perhaps it could have been admitted. But, as if often the case, pro se defendants are usually not articulate enough to set forth a legally relevant reason that evidence should be admitted. Unless the defendant could show that the video showed something allowing a jury to determine whether or not the law was violated, it probably wouldn't be relevant and I can't easily imagine how it would be relevant, but perhaps there was some special facts or circumstances that might show, for example, that the speed gun was actually picking up another vehicle.
It is hard to measure accuracy in absolute terms because figuring out the truth is the problem that trials seek to solve in the first place. This is especially true of cases that go to trial. Cases that are almost sure to be resolved one way or the other by any tier of fact generally plea bargain (in criminal cases) or settle prior to trial (in civil cases). The plea bargaining rate is 90%-95% in criminal cases and less than 5% of civil cases go to trial. For better or for worse, civil jury trial have become much less common in the last half century, while criminal jury trial rates have been comparatively much more stable (criminal jury trials have become increasingly less common in federal trial courts, however, where the rate at which criminal cases go to trial is about half that of state courts). The good news is that this suggests that the accuracy of the entire process acting in the shadow of trial in most cases, is much greater than the accuracy of trials themselves, which tend to involve the hardest and closest cases. The bad news is that to the extent that trial outcomes are unpredictable, even those who are innocent or not at fault in a civil case, will sometimes reach an unfair agreed plea bargain or settlement. As a 1992 law review article comparing outcomes in civil cases between judges and juries notes, &quot;The empirical results prove resistant to simple explanations.&quot; Some key studies summarized here concluded that: The judge and jury in the Kalven-Zeisel survey of 3,500 criminal cases agreed in 78% of the cases on whether or not to convict. When they disagreed, the judge would have convicted when the jury acquitted in 19% of the cases, and the jury convicted when the judge would have acquitted in 3% of the cases—a net leniency rate of 16%. Disagreement rates were no higher when the judge characterized the evidence as difficult than when the judge characterized it as easy, suggesting that the disagreements were not produced by the jury’s inability to understand the evidence. Disagreement rates did rise when the judge characterized the evidence as close rather than clear, indicating that disagreement cases were, at least in the judge’s view, more likely to be those cases that were susceptible to more than one defensible verdict. Primary explanations offered for the overall differences were differences in judgments about the credibility of witnesses and a different threshold of reasonable doubt. Two smaller, more recent studies using the Kalven-Zeisel method have shown remarkably similar patterns in criminal cases, obtaining 74% to 75% agreement, with a greater leniency of 13% to 20% from the jury. Studies outside the United States have shown similarly high levels of agreement between professionals and juries or lay judges in criminal cases. For the 4,000 civil trials in their judicial survey, Kalven and Zeisel obtained the same agreement rate of 78% on liability, but disagreement was almost equally divided, so that in 12% of the cases, the jury found for the plaintiff, while the judge favored the defense and in 10% of the cases, the jury found for the defense, while the judge would have made an award. Awards by juries were 20% higher on average than awards by judges. Several smaller, recent studies of civil jury cases in several locations have indicated agreement rates on liability between 63% and 77%, but it is unclear whether any overall change has occurred over time because no national study comparable with the Kalven and Zeisel study has been conducted. Because punitive damages are awarded so rarely (in roughly 3% of contract and tort cases), researchers conducting case-specific judicial surveys have not been able to compare judge and jury decisions on punitive damages. While the discrepancy between judges and juries in criminal cases (one in six cases) is quite large, this suggests that no more than 1-1.5% of criminal defendants charged with felonies in the system as a whole are inappropriately acquitted by juries, and that no more than about 0.16% of criminal defendants charged with felonies are wrongfully convicted by judges (since only about 10% of criminal trials in the U.S. are bench trials). Moreover, as discussed below, the &quot;inappropriate acquittal&quot; by juries rate as a share of system-wide felony cases is probably lower because there are good reasons to think that the higher conviction rate in bench trials than in jury trials has more to do with the biases of judges than with more accurate fact finding by judges. A 2010 empirical study looking at the impact of the racial composition of juries on the likelihood of convictions in felony cases in a Florida county found that statistically, a similar number of felony cases (82%) that go to trial are &quot;easy&quot; cases in which any finder of fact would reach the same result, but that the acquittal rate in other cases varied dramatically based upon the racial composition of the jury. This study provides further support for the hypothesis that close cases are more strongly influenced by the implicit biases of the fact finders than by their capacity to assess the facts accurately. Incidentally, this higher conviction rate is not particular to the United States, it has also been true historically in Japan during periods when it had a jury trial system, even though its legal codes use German legal codes as a starting point. I have personally had discussions with several South Korean and Japanese judges (while I was in law school and they were pursuing graduate law degrees in the U.S. while on sabbatical from their judicial positions) who say that they have a policy of alway believing the prosecutors in criminal cases and assuming as a starting point, at least, that any defense testimony that contradicts the prosecution's case is a result of lies by the defense witnesses, which doesn't speak highly for the accuracy of bench trials in criminal cases in those countries. An experienced judge argued in a law review article in the late 1980s based upon his lengthy career presiding over jury trials, that juries were more accurate. Probably the strongest argument he makes is that judges are prone to bias, in part, though what many people would now call the process of regulatory capture. Other experienced trial judges echo this positive assessment of juries as noted in a 2012 article, for example, noting that juries are often better grounded in the reality of everyday life and in community standards than judges. A 2007 study (full text here) reached a conclusion on the accuracy of jury trials in criminal cases based upon the a priori assumption that judges are at least as accurate as juries, which isn't helpful at resolving your question because it assumes the answer rather than proving it, but does shed some light on the minimum extent to which one or the other triers of fact would have reached the wrong conclusion: A new Northwestern University study shows that juries in criminal cases are reaching incorrect verdicts. The study, which looked at 271 cases in four areas of Illinois, found that as many as one in eight juries is making the wrong decision – by convicting an innocent person or acquitting a guilty one. In each case, while the jury deliberated, the judge filled out a questionnaire detailing what his or her verdict would have been had it been a bench trial. The verdicts only matched in 77 percent of cases. The study assumed that judges are at least as likely as a jury to make a correct verdict, leading to the conclusion that juries are only correct 87 percent of the time or less. The study was conducted by Bruce Spencer, a Northwestern statistics professor, and will be published in the July issue of the Journal of Empirical Legal Studies. Spencer said in a statement that it would take a much larger study to truly predict the accuracy of jury verdicts nationwide in all cases. The same 2007 study is also critically analyzed here, and notes that judges again are more likely to convict than juries in cases where defendants opt for jury trials (which they do about 90% of the time in criminal cases in state courts). A different 2007 study used evidence mostly derived from DNA based exonerations in capital rape-murder cases from the 1980s to conclude that the wrongful conviction rate in those cases following jury trials is 3.3% to 5%. Given that judges are much less likely to acquit than juries, this strongly suggests that the wrongful conviction rate for bench trials in serious criminal cases would be much higher than it is in jury trials. The methodology of the study doesn't make it possible to estimate the wrongful acquittal rate in jury trials which is further muddied by the question of the extent to which jury nullification, in the form of an acquittal of someone who is actually guilty beyond a reasonable doubt, is a legitimate exercise of mercy or is problematic - something also influenced by perceptions of where jury nullification is most common (e.g. this may disproportionately benefit police tried for crimes allegedly committed while carrying out their duties). It is worth noting, however, that juries in capital cases (i.e. those where the death penalty is a potential sentence) are systemically less pro-defendant than other juries because they are &quot;death qualified&quot; which is to say that people opposed to the death penalty are systemically removed for cause from the jury pool, which makes juries in capital cases more likely to convict than juries in other cases. This means that it is also probably likely that wrongful conviction rates are higher in capital cases than in other cases. Indeed, one reason that prosecutors choose to bring death penalty charges in a case is to increase the odds that a defendant will plea bargain to avoid the risk of the death penalty, and to increase the odds that the defendant will be convicted at trial, in a criminal prosecution where the evidence is factually weak compared to a typical felony case that prosecutors would bring. Yet another 2007 study concluded that: Drawing on a sample of 798 Ohio criminal justice professionals (police, prosecutors, defense attorneys, judges), the authors examine respondents’ perceptions regarding the frequency of system errors (i.e., professional error and misconduct suggested by previous research to be associated with wrongful conviction), and wrongful felony conviction. Results indicate that respondents perceive system errors to occur more than infrequently but less than moderately frequent. Respondents also perceive that wrongful felony conviction occurs in their own jurisdictions in .5% to 1% of all felony cases, and in the United States in 1% to 3% of all felony cases. Respondents, however, specify an acceptable rate of wrongful conviction to be less than .5%. A replication of this study with a survey of comparable Michigan officials published in 2008 gave rise to almost identical results. The review of literature in the 2007 paper surveying Ohio officials also notes the notable fact that 7% of convicted felons whose convictions are reversed on appeal and who are then retried before a new jury are acquitted (I don't have data breaking out the retrial results for capital convictions that are reversed on appeal and retried easily at hand right now), which provides another order of magnitude estimate of the reliability of jury trials (although, of course, cases reversed on appeal are by definition cases whose verdicts are not reliable for some specified reason, relative to cases in which convictions are not appealed or are affirmed on appeal). About 40% of criminal convictions following a trial are appealed (the appeal rate is very nearly 100% in death penalty cases). This is much higher than the rate of appeals of civil jury verdicts, in part, because convicted criminal defendants who cannot afford a lawyer are entitled to a direct appeal at state expense (although it can be pointless to do so if you already have a felony criminal record, you are likely to be released before the appeal is ruled upon after considering your sentence and time served, and your prospects of success on appeal are poor, which is the case in many minor felonies). About 8% of cases appealed in criminal cases result in a reversal of at least part of a trial court decision (although the figure is about 19% in death penalty cases). So, the odds of a criminal conviction following a trial being appealed, reversed on appeal, and then retried resulting in a conviction is roughly 0.2% (one in five hundred). There is also considerable evidence to support the hypothesis that certain facts patterns are much more prone to producing wrongful convictions than others. For example, excessive faith in eye witness identification of defendants (especially in cases of white witnesses identifying black defendants who are strangers to the witness) and scientifically unsound forms of expert testimony are particularly common causes of wrongful convictions. A 2010 review article examining 100 years of research on the question of wrongful conviction notes that &quot;traditional sources of error (eyewitness misidentification, false confessions, perjured testimony, forensic error, tunnel vision, prosecutorial misconduct, ineffective assistance of counsel, etc.) are contributing sources, not exclusive causes, of wrongful convictions.&quot; A 1998 law review article looks at a small sample of convictions allegedly obtained with false confessions and also examines the tricky question of what &quot;innocence&quot; and a &quot;wrongful conviction&quot; really mean. For example, suppose that someone falsely confesses to facts that would make him guilty of first degree murder when in fact he was actually an accessory to manslaughter. He isn't truly &quot;innocent&quot; of any crime related to the death in question, but is likely to be convicted of a crime much more serious than the crime of which he is actually guilty. A 2006 law review article examining a single case in detail in the context of broader research finings comes to similar conclusions about high risk fact patterns, but throws in another - clusters of mass wrongful convictions driven by one or many deeply corrupt police officers in a single department who routinely lie and falsify evidence to obtain large numbers of wrongful convictions. A Wall Street Journal blog post from July 16, 2017 cites a Journal of Empirical Legal Research article in support of the proposition that juries get about one in six criminal cases wrong and that judges do only slightly better. Some studies have looked at indications that judges are not better than juries at accurately reaching correct outcomes that don't look at the actual outcomes themselves: In study after study, researchers have found more similarities than differences (see Robbennolt, 2006; Rowland, et al., 2010). For example: Retired judges were no better than college sophomores, teachers and other novices at spotting witness mendacity. Retired judges were no better than mock jurors at ignoring inadmissible evidence. Retired judges evince no greater understanding of the scientific principles underlying Daubert standards than do mock jurors. Moreover, social science research makes it very clear that many decisions by trial judges, federal and state, are affected by extra-legal political influences. For example: The decisions of Federal district judges, usually thought to be better trained and less susceptible to extra-legal influences than are their state counterparts, can for many case types (e.g., abortion) be predicted at a high rate of accuracy simply by knowing the judge’s appointing president. Elected state judges’ sentencing decisions change in tandem with the proximity of elections A comprehensive review of prior studies in a 2005 article reiterates almost all of the conclusions from various kinds of data reached above - i.e. juries are more lenient but their skills at assessing facts are similar to those of judges. Arguments For And Against The Jury System Unrelated To Their Accuracy A 2011 law review article reiterates that judges are far more likely to convict that juries, on average, which it argues is good even if it comes at the expense of lower accuracy. This article does not squarely address the real money question of whether judges or juries are more accurate in their decisions to convict or acquit defendants. The author argues that certainty of punishment is more important to deterring bad conduct than sentence length or the accuracy of the process. A 1981 article by John Langbein, one of the leading scholars in the field of comparing the European legal system (where serious criminal trials often involve &quot;mixed courts&quot; with a judge and lay judges serving together in a capacity that isn't quite a true American style jury) to the American legal system concluded that: The conclusion is that the mixed court serves the jury policies well, though not fully; and that it is a superior alternative to the indigenous nontrial devices-plea bargaining and bench trial-that have displaced the jury from routine American practice. It is also worth noting that one of the important justifications for using jury trials rather than bench trials or mixed trials, is that it enhances the institutional legitimacy of the judiciary, regardless of its accuracy, in a system where both triers of fact sometimes make mistakes. This is because in a jury trial system, an outcome that is perceived as incorrect can be blamed on the diffuse and effectively anonymous jury who cannot be held accountable, deflecting blame from judges who could be held accountable or whose bad decisions would reflect poorly on the judiciary, or the judge in question at least. It is easier to support the legitimacy of the judicial system if judges are rarely blamed for reaching the hard verdict in high stakes cases. Also, since juries deliver only a verdict, and not a detailed justification for their ruling as a judge in a bench trial must, the jury verdict, while less transparent, does allow people who might potentially agree with the result even if they wouldn't have agreed with the means by which that particular jury actually reached its decision, to give the jury the benefit of the doubt, again increasing popular acceptance of the result.
Are defendants legally obliged to provide all culpatory evidence to prosecution? The question here is whether or not all evidence requested by prosecution must be provided by the defense? If the defense plans on only using the evidence of the prosecution, does the prosecution get to demand evidence the defense would rather not release? No. Usually only specific kinds of evidence related to specific kinds of claims such as alibi evidence, an insanity claim, or expert testimony must be disclosed prior to trial by a defendant in a criminal case. A defendant in a criminal case does not have to disclose evidence harmful to the defendant's case prior to trial as a general rule. Sometimes there is a requirement to disclose witnesses anticipated to be called, or exhibits to be possibly used very shortly prior to trial, but that is more the exception than the rule. Does the answer depend on the whether or not the case is criminal or civil? Yes. A plaintiff in a civil case can compel disclosure prior to trial of all evidence in the custody, control, or possession of the defendant that is relevant or is reasonably calculated to be relevant to a disputed issue identified in the complaint, answer, and other pleadings (e.g. counterclaims, replies to counterclaims, third-party complaints, cross-claims, etc.). The scope of discovery is slightly different in jurisdictions that don't follow the federal model. This can include pre-trial depositions of the parties, although a defendant can claim the 5th Amendment at the risk of being exposed to an adverse inference communicated to the jury at trial if the defendant does so. Furthermore, most jurisdictions require the pre-trial disclosure of expert testimony that will be used at trial, of exhibits that will or may be used at trial, of witnesses who will or may be called a trial, of all documents that are relevant to a disputed issue identified in the complaint, answer, and other pleadings, of all insurance coverage that could cover the claim, of all persons with knowledge of the disputed facts, and of an expected damages calculation. In the federal system, however, one need pro-actively disclose only witnesses and documents that support your case without being asked. Is there consistency on this or is it at the discretion of the judge? The rules of procedure applicable to a case govern the scope of discovery, but judges have considerable discretion to determine that requests are excessive relative to what is at stake in the case, are irrelevant, or unduly burden some other legitimate interest of the person subject to discovery. Is there punishment for non-compliance? Yes. First of all, a failure to disclose when there is a duty to do so is a ground to exclude presentation of that evidence at trial. Secondly, in civil cases, attorney fees incurred to obtain the discovery can be awarded, facts that might have been disclosed can be declared to be true as a matter of judicial sanction where there is not disclosure, claims can be dismissed, etc. The main relevant federal rule in civil cases is Federal Rule of Civil Procedure 37. It is an unlawful request that must nonetheless be followed with only a hypothetical remedy left to the defendant as is the case in most of these united states to comply with an obviously unlawful arrest that doesn't present an immediate threat to life? I don't understand this long and convoluted sentence. The part about an unlawful arrest seems divorced from the issues in the rest of the the question. It isn't clear what kind of unlawful request is involved either.
There is virtually no chance this would be admissible. When a defendant argues that abuse at the hands of third party led to a mental defect that excuses her from culpability, the prosecution is free to rebut that argument. However, the prosecution's evidence must be relevant, i.e., it must have a tendency to make a fact of consequence more or less likely to be true. Here, none of the proffered evidence has any real bearing on any fact of consequence: The fact that the defendant is taller than the alleged abuser does not make it less likely that the defendant was abused. The fact that the defendant's &quot;fake&quot; voice (what does that even mean?) is deeper than the alleged abuser's does not make it less likely that the defendant was abused. The fact that young white women have more Tinder matches than middle-aged Indian men does not make it less likely that the defendant was abused. Even if you could find some thin reed on which to hang the relevance of these racial and gender stereotypes, the evidence would likely still be excluded under Rule 403, as the probative value would be so trivial that it would be outweighed by the likelihood of unfair prejudice or misleading the jury.
Prosecutions for falsely reporting rape are at least as common as perjury convictions (and usually don't count as perjury since the initial report is rarely made under oath), and even when charges are brought by prosecutors involving false statements made under oath, prosecutors tend to favor lesser misdemeanor false reporting charges over perjury charges. See, e.g., cases with news reports of such cases in Colorado and Wyoming on May 24, 2021, September 11, 2015, August 29, 2014, and March 18, 2008. This isn't to say that these cases are terribly common although they tend to generate headlines when they are brought. The State of Colorado commenced 1,801 felony sex offense cases in the 2021 fiscal year, for example, which was not atypical, and false reporting of sex offense cases are brought in Colorado maybe once every year or two. The conviction rate in sex offense cases that are prosecuted isn't 100%, but something on the order of 90%-95% of sex offense cases result in a guilty plea, and well over half of the remaining cases result in convictions at trial. As an order of magnitude estimate, perhaps one in fifty to one in two hundred cases where sex offense charges are pursued, but there is not a conviction, gives rise to false reporting charges against the alleged victim. Many acquittals and dismissals of charges that do occur are best characterized as cases where there is a reasonable doubt because jurors believe that it is reasonably possible that there may have been a good faith witness misidentification, or because charges were dismissed because a confession or evidence obtained in a search was unlawfully obtained and had to be suppressed. It would be very rare for a defendant to be acquitted (after a judge in a preliminary hearing found that probable cause was present) because the jury believed that the testimony of a victim was believed to be intentionally false, and there is no way to tell from the verdict itself that the jury reached this conclusion. The problematic aspect of charges of false reporting of sex offenses is the there have been famous instances of women being convicted for falsely reporting rape (see also here focusing on a different case), only to subsequently have the allegations for which the victims were punished confirmed to be true with DNA and other evidence. The number of cases where true allegations of sex offenses are made but not pursued because law enforcement finds the allegations to not be credible, almost surely greatly exceeds the number of cases where false reports of sex offenses are made to police, although this ratio varies greatly from one police department to another based upon the institutional culture of the police department in question.
There actually is a practical effect to a "not proven" v. "not guilty" verdict in Scotland, but it is mostly sociological or social in nature rather than legal. If your question is, are there future legal concerns, than no. Not proven is, to be sure, an acquittal. However, it is an acquittal that the tells the public something important: that the trier(s) of fact thought the person likely guilty. That's a fairly substantial distinction. In Scotland, a criminal case may be decided either "in solemn procedure", which is simply the Scot term for a jury trial v. "in summary" or in "summary procedure" which is the U.S. equivalent of a bench trial. The difference between the two (and the divergence from the U.S. procedural vehicle) is that for lesser crimes the accused doesn't have an automatic right of a jury trial for any criminal matter. In some ways this lesser included makes up for the fact that the Scottish accused is without absolute right to choose jury or bench trial, which in the U.S. can be very meaningful from a tactical perspective. Think of how important the make-up and emotional proclivities of juries are to both convictions and acquittals. A bench trial can be beneficial to the truly unlikable defendant, or in especially brutal crimes, where juries may convict out of fear or sympathy for the victim, even if the case is weak. At the same time, they may nullify the conviction for the sympathetic defendant. Juries are notoriously emotional and bias driven. Being able to choose a bench trial where the judge will follow the evidence and avoid the emotional response of a jury can be invaluable. Just as a sympathetic defendant can appeal to the emotions of the jury for acquittal or jury nullification, on the opposite spectrum. In Scotland, lesser crimes are always (with limited exclusions) tried by a judge, while more serious allegations always (again w/ limited exclusions) get a jury trial, automatically. The defendant does not choose the type of trial he is afforded. Hence, a defense or a prosecution cannot fiddle with the balance of proof based on emotion or lack there of. They get what they get. There are various rules procedurally that differ in comparison, but since this isn't the question that is the general rule and should suffice for background. Also hugely important is the fact that in Scotland, jurors decide a case by majority vote (like a civil trial in the U.S.); hence, there are no hung juries and they don't need a consensus. So, one way or another the verdict will be given in a Scottish criminal action. Scots also get comparatively huge juries to any other country (15 jurors) and they only need 8 in agreement to reach a verdict. Tactically, the "not proven" is a lesser included verdict (like U.S. uses lesser included charges in cases that are weaker for the prosecution). This lesser included finding can be used by choice when the Prosecution has a sympathetic defendant or when the defendant is probably guilty or unlikable. If the jury thinks the defendant (called "accused") probably did the crime, but the prosecution has failed to prove the elements, they can/will issue a "not proven" verdict. This sends a big message. This, again, is typically only reserved for those cases when there is strong but not conclusive proof that someone committed a crime. They don't want to profess their innocence with a not guilty verdict, so they are still acquitted, but with he stigma of the "not proven" verdict attached. Some estimates have from 1/5 to a full 1/3 of all acquittal verdicts by Scottish juries as "not proven" as opposed to "not guilty". Not proven can also be used by judges in the bench trial (summary procedure), however it's much less common. The proportion of 'not proven" acquittals in general is higher in the more severe cases; but so then are the proportion of acquittals versus convictions. These would likely be hung juries in the U.S.. Both in the "solemn" and the "summary" acquittals, not proven is interpreted as indicating that the jury or judge, respectively, is not convinced of the innocence of the accused; in fact, they may be morally or even factually convinced that the accused is guilty, but do not find the proofs sufficient for a conviction under the elements of the crime on the jury instruction/verdict form. I look at this as similar to the adage oft used in the U.S., which is an acquittal, despite the fact that the verdict is termed "not guilty" does by no means indicate the person is in fact "not guilty", it just means the prosecution couldn't prove its case. Sociologists in the U.S., as well as legal scholars, have studied the phenomenon, and it appears that most not guilty verdicts in fact let go a guilty person. This can be intuited by the evidence the jury never saw, either by suppression from bad searches, by the exclusion of witness testimony due to procedural rules like hearsay, privilege, etc., and other forms of keeping relevant evidence from the jury to protect the rights of the accused. But in the U.S. the person can go forth and say, "Hey, I was proven not guilty!" Scotland also has another interesting rule of criminal procedure, whereby a criminal can't be convicted without corroborated evidence. What this means is that if all the prosecution has is the victim witness, by way of proof, testifying, and no physical or corroboration testimony, Scottish law requires acquittal, but often will be so by the verdict "not proven". This is huge, if you think about it. Use, for example, a rape trial. A woman testifies, saying that Joe Schmoe climbed through her window and raped her. She knows Joe - he's her neighbor. Nobody saw him climb in. But she knows it's him. He leaves no physical evidence, having shaved his entire body and used appropriate protection (gloves, condemn, etc.). She has a rape kit done. Rape is obvious, but the only proof is her testimony. Joe goes free. But in Scotland, he goes free with a stigma attached. He's found "not proven" rather than "not guilty". I think this corroboration rule has a lot to do with why this verdict system still exists. In the U.S. the trier of fact would weigh the testimony and decide if one person was substantially more believable than the other, and a verdict would issue. That is a substantial difference, procedurally. Since Scotland doesn't have the hung jury because there is no consensus required they use the "not proven" in the same way a U.S. jury uses the hung jury when one or more jurors thinks the prosecution didn't prove their case but it's fairly clear the defendant is, in fact guilty. Then, you will often get a "hold out" juror, and since the U.S. requires a unanimous verdict, the hold out hangs the jury. It's sort of the opposite of jury nullification. The person knows that the evidence fell short, but their conscience can't reconcile letting the person go free, so they will vote guilty to hang the jury, almost ensuring the prosecution gets another shot. There has been a lot of debate about this three verdict system in comparative law circles, with many legal scholars saying it's antiquated. But I think it serves an important purpose. It carries the stigma of likely guilt for those people who probably committed the crime but got off. Further, the hung jury cost tax payers millions of dollars in the U.S., and this is often the side effect of people not wanting there to be absolutely no recognition of the fact that the accused probably committed (especially serious) crime(s). The Scots, on the other hand, have found away to accomplish this without the cost and emotional toll multiple trials takes on all the players involved, from witnesses and victims, their families, the accused, and even the lawyers and the prosecutions, who have to put in all the work of a trial just to start anew. Here is a really good scholarly article that deals with this interesting phenomenon not seen in (I don't believe) any other country: https://journals.iupui.edu/index.php/iiclr/article/viewFile/17848/18019
Focusing on the part of the question where you say But my question relates to &quot;evidence.&quot; That is, does &quot;admissible evidence&quot; have to be of the same or different standard in a civil versus criminal case there can be (are) some differences in admissibility between civil and criminal cases. Looking at the Federal Rules of Evidence, FRE 412, one cannot introduce &quot;evidence offered to prove that a victim engaged in other sexual behavior; or evidence offered to prove a victim’s sexual predisposition&quot;, but distinct criminal vs. civil exceptions exist. For criminal cases, The court may admit the following evidence in a criminal case: (A) evidence of specific instances of a victim’s sexual behavior, if offered to prove that someone other than the defendant was the source of semen, injury, or other physical evidence; (B) evidence of specific instances of a victim’s sexual behavior with respect to the person accused of the sexual misconduct, if offered by the defendant to prove consent or if offered by the prosecutor; and (C) evidence whose exclusion would violate the defendant’s constitutional rights. but in civil cases, In a civil case, the court may admit evidence offered to prove a victim’s sexual behavior or sexual predisposition if its probative value substantially outweighs the danger of harm to any victim and of unfair prejudice to any party. The court may admit evidence of a victim’s reputation only if the victim has placed it in controversy. Also, under FRE 601, Every person is competent to be a witness unless these rules provide otherwise. But in a civil case, state law governs the witness’s competency regarding a claim or defense for which state law supplies the rule of decision. which introduces an asymmetry between the two kinds of cases. There are also standards of admissibility that only apply to criminal cases and not civil ones (FRE 413, FRE 414) or only in civil cases (FRE 415)