What&#39;s stopping someone from saying &quot;I don&#39;t remember&quot;? There are (at least) two problems possibly stemming from a person testifying in court: If they tell the truth, the testimony may have negative consequences they potentially don't like (which is the whole point of 5th Amendment, when the testimony is by the accused or in general detrimental to person testifying). If they lie, they can be convicted of perjury, which is a nice fallback when you don't care about actual crime but about getting the person damaged at least somehow - US history and especially politics is littered by people who were gotcha-ed by perjury charges and not main charges. If that is the case, then what prevents such a person from simply saying &quot;I do not remember&quot; when testifying? You can't prove a negative, so they can't be convicted of perjury for lying about whether they remember; they didn't testify about any fact so they can't perjure themselves; and they didn't help the prosecution (or defense) by truth.
You can't prove a negative, so they can't be convicted of perjury for lying about whether they remember; Yes, they can. The government can convict the witness of perjury by proving that they did remember. This may be difficult, but it's not impossible. Now you may say that we can't ever prove with certainty what a person did or didn't remember. But the legal standard isn't certainty, it's beyond a reasonable doubt. So a jury is allowed to draw a reasonable inference about whether they remembered, based on evidence of their outward behavior and other circumstances. As an extreme example, suppose Alice was overheard chatting freely about topic X an hour before the trial, but when asked about topic X on the stand, said she didn't remember. When presented with evidence of her earlier conversation, a jury could reasonably infer that she was lying about not remembering. Is it possible that she truly had a memory lapse in the intervening hour? Sure, anything is possible. Is it reasonable to believe that she did? Probably not. The US Department of Justice's Criminal Resource Manual has this to say on the subject: Witnesses who claim not to remember, rather than deny a fact, may be prosecuted for perjury. However, the government must prove both that the witness at one time knew the fact and that the witness must have remembered it at the time he or she testified. United States v. Chen, 933 F.2d 793, 795 (9th Cir. 1991). If the dates of the transaction and testimony are sufficiently close, memory may be inferred. Instances in which the witness remembered other events that occurred at the same time or earlier than the event in question, or mentioned the event either immediately before or after his testimony, would be probative of the witness's memory at the time of the testimony. The two witness rule does not apply to prosecutions based on false memory lapses, and circumstantial evidence is sufficient, since there is no direct evidence possible concerning what the defendant actually believed. Gebhard v. United States, 422 F.2d 281, 287 (9th Cir. 1970). There's a similar issue in all laws that deal with a person's knowledge or intent. Suppose Alice hits Bob with a stick and he dies. To convict Alice of murder, it must be proved that by hitting Bob, she intended to kill him. Can we ever really know what was in her heart? Maybe not, but if there is evidence that shortly beforehand, she told someone that she was going to kill Bob, it would be a reasonable inference that this was her intention.
The Fifth Amendment would not apply, because nothing in the testimony would incriminate the doctor. Indeed nothing would be at all likely to incriminate the President either, it is not a crime to be unable to carry out Presidential duties. It is likely in such a case that the President would waive confidentiality. In that case the doctor could testify freely. If the President insisted on confidentiality, and attempted to prevent the doctor from testifying to Congress, there would be a conflict between the power of Congress to compel testimony, in this case on what is clearly a vital national issue within the scope of the needs of Congress, and traditional doctor-patient confidentiality, let alone the requirements of HIPAA. I am not sure how this conflict would be resolved. There might be an emergency application to the Supreme Court, but the SC does not usually do very well with truly urgent issues. The Pentagon Papers case and Bush V. Gore indicate some of the problems that can arise. If the doctor was prevented from testifying, that might incline members of congress to think the testimony would not be favorable to the President, and thus tend to suggest that they should not approve the President resuming or continuing his or her powers and duties. But that is rather speculative. The 25th has never been invoked, and the detailed procedure that would be followed if it were is not very clear. I am not aware of any similar situation in which medical testimony has been demanded to deal with an urgent issue, but the patient has attempted to block it. I think this case must be considered to be undecided until it actually arises and a court rules.
The citation could be written but it should be easy to beat. In the circumstance that you describe the accused could just say the he was not driving his car at the time. If the prosecution is a sham with all your friends saying you all saw this thing, then the defendant can bring all of his friends to say that he was at some other place. The benefit to having a cop on the scene is that the cop will get ID and positive identification. The other thing the cop has is expert judgment. If a cop sees unsafe lane movement and writes a ticket, his testimony in court carries more weight than the "it was not unsafe!" testimony of the accused. Keep in mind, getting all of your witnesses to court on the same day, after continuances and other delays, and getting them all to tell the same story to overcome the presumption of innocence is no small feat. All that to say, it's easier with police as witness. There are two mechanisms which could get you where you want to go. Private prosecution and citizen's arrest. Private prosecutions are a part of history but not strictly unavailable at the state level. You could write up some charging documents to see if you can get your target indicted. Citizen's arrest is interesting because the rules are fairly unclear unless governed by a specific statute. There are two necessary parts of citizens arrest and the first part gets the attention. The first part is the detention (arrest). The crimes for which a citizen can legally detain a suspect are likely defined by state statute. The second part is giving testimony about the witnessed crime. Let's assume that you see a felony happen and watch the perp walk into a gas station bathroom. You are prepared to arrest, do part number one, and then call the cops, to do part number two. But while you wait for the guy to come out of the bathroom a cop walks up. You explain the felony and the cop goes into the bathroom and arrests the guy. It's purely witness testimony that led to the arrest and the indictment (physical evidence - let's say there is none) and even the trial. You successfully get the guy indicted and when you show up to testify you tell the story as you witnessed it. Now the accused gets to take the stand. When he takes the stand he says, "it was the other guy." When asked, "what other guy?" He says, "I was in the bathroom and a guy ran in and went into the stall. Then a cop came in and arrested me." Reasonable doubt right there. How much more if it's a bunch of friends ratting on some lone driver? Police need evidence. Prosecutors need evidence. Judges need evidence.
united-states It is not required for a person to formally assert a fifth- or a first-amendment right when questioned by the police. One can simply be silent, refuse to answer any questions, without giving any reasons. But probably more effective and just as legal is to say &quot;I won't answer any questions until I have talked with a lawyer. I want a lawyer, now.&quot; That is perhaps less likely than using the words &quot;plead the fifth&quot; to be assumed to be a confession of guilt, although some people and some police may take almost anything as a confession of guilt. By the way some of the points you distilled from the video (which I have not watched yet) are correct, some are half-truths, and some are quite incorrect. For example: The 5th amendment was not designed as a shelter for the guilty (despite it often being used as such). It was designed to help prevent you from unknowingly incriminating yourself. As a matter of history, this is quite incorrect. It arose historically out of a reaction to government procedures deemed oppressive. See https://law.stackexchange.com/a/63690/17500 for more detail. But helping people avoid unintentionally incriminating themselves is one of its major current functions. You can't talk your way out of getting arrested. Sometimes you can, but it is never safe to count on it. You can't know in advance if it will work, and more often than not it doesn't. Everything you tell the police can be used against you but not to help you. Not quite. If your statement is recorded, as is likely nowadays, the whole statement must be given to your lawyer and entered into evidence if you are eventually charged. (See Brady vs Maryland) Things said in your own favor may be discounted as self-serving, but the judge and jury will still hear them. But they can be very risky.
If someone testifying before congress refuses to respond to appropriate questions (questions within the scope of the congressional inquiry), that person can be cited for contempt of Congress. One way to avoid this is if the witness can invoke the Fifth Amendment privilege against self-incrimination. That says that a person may not be compelled to be a witness against himself (or herself) in a criminal case, and has been interpreted to mean that if testimony might in future be used against the witness in a criminal case, it cannot be required, even if the current occasion is not a criminal case. However, if a person has been granted immunity in a particular matter, no testimony can be used against the person in a criminal case on that matter, and so there is no Fifth Amendment privilege not to testify on that matter. This applies to testimony before a court as well as before Congress. The grant of immunity must be at least as comprehensive as the refusal to testify would have been, or the privilege remains. Therefore, if a person has been granted immunity on a subject, that person cannot refuse to testify before Congress by invoking the Fifth Amendment. If the person does refuse, s/he can be cited for contempt of Congress. However, the person can raise a claim that the inquiry was not a proper one, for example because the subject was not a proper one fo Congressional inquiry, or that the Committee was not properly authorized. If the court upholds such a claim, the person will not be convicted of contempt. Also, while Congress can issue a citation, the Justice Department is not required to prosecute the person, and may choose to let the issue drop. Or the court might not convict on some other ground. And of course Congress (or one house of it) has to vote to issue the citation, which it might decide not to do, for political reasons, or indeed for any reason at all. So a grant of immunity alone is not enough to say that testimony will be compelled, but it is a significant step towards such compulsion. Note that under Murphy v. Waterfront Comm'n, 378 U. S. 52 (1964), a state grant of immunity also bars Federal use of the compelled testimony or its fruits, and under Kastigar v. United States, 406 U.S. 441 (1972) a Federal grant of immunity bars state use of the compelled testimony or its fruits. See also This Justia essay on "the Power to Compel Testimony" which covers the whole subject with multiple case citations.
There are certain situations where the law may require you to provide some information -- particularly when you've been pulled over for a traffic violation -- but it is typically limited to basic identifying information. Beyond that, it is legally advantageous to refuse to answer questions. If you are doing so, though, you should explicitly invoke your Fifth Amendment right against self-incrimination, and your Sixth Amendment right to counsel. Invoking the Fifth prevents the police from using your refusal to answer as evidence, and invoking the Sixth requires the police to stop asking you questions. It may, however, be practically disadvantageous to refuse to answer questions, as there are cops who are just looking for a reason to act like a psychopath.
Basically, it is up to the court. The relevant law is the Police and Criminal Evidence Act (PACE). You don't give much in the way of specifics, but it sounds like you confessed something to the police at the side of the road immediately after the accident, and now wish to dispute that confession. If you are taken to court and the police want to introduce your confession as evidence then you (through your lawyer) can ask the court to rule it out. You may be able to do so on a number of grounds. Was the confession properly recorded at the time? Were you treated in an oppressive manner, such that you felt you had to say what the police wanted to hear. Did you think you might get more favourable treatment if you said what the police wanted? For instance, did you think you might be allowed to go home once they were satisfied? Were you given a proper rest, or were you in a mental state that might cause you to say things without understanding the consequences (it sounds like this would be your main argument, but consider the others too). [Edit] If you needed medical treatment that would also be relevant. Were you properly cautioned (that speech beginning "You do not have to say anything...") before the police asked you questions. If you think you may be facing criminal charges then you should get yourself a lawyer sooner rather than later. A lawyer will know all about this and be able to navigate the relevant legal processes on your behalf. A bit of background: back in the 1970s the police frequently attributed incriminating statements to suspects when arrested, such as "Its a fair cop, guv", or "Who ratted on us?". The rules in PACE were made to stop such "verballing".
Is it possible for a witness to backtrack and claim that their previous statements were wrong because they misremembered? ... Is the witness now allowed to say something along the lines: &quot;Huh. That's odd. I clearly remember it differently. But it's such a small detail and it was so long ago...&quot;? Yes. Or is it now considered a deliberate lie? A judge's assessment of a witness's credibility and reliability is much more nuanced. See &quot;How is a judge to evaluate a witness's credibility?&quot;