In US, does an investigator always present the evidence of guilt of a suspect no matter what? In US criminal justice system, must the investigator always provide the evidence that the particular suspect is the one who indeed perpetrated the crime, no matter what investigation procedures and assets were used(access to a particular computer system or software, access to encryption keys, IP logs, etc.)? I ask such goofy questions because US has so many interesting laws that make nonsense to me and this is the reason why I ask some of the basics which should make sense in any justice system.
So typically, in the U.S., the investigators (police) will give the case to a prosecutor who will review the case and the evidence and decide if they will present the case to a judge and if so, what will be charged. The prosecutor is the ultimate authority of how to present the case to the court. The investigator(s) will likely be called to testify as their expertise's and actions that lead to certain evidence is required. If there is a certain expert in some type of evidence, that person may testify on conclusions of their findings (for example, if the coroner's report concluded that some was the victim of a homicide, the coroner who wrote the report will be called in to testify to his findings... but since the coroner did not have access to the Detective's witness, they wouldn't talk about the evidence with respect to that which came from eye-witness statements. If you're basing you question off of TV or Film depictions of Court rooms, keep in mind that many court room scenes are not accurate and the investigator presenting all of the case could be a result of a limited cast, budget, or time for specialists to present the case. Some shows explicitly separate the roles (Law and Order and its spin offs are a one-hour shows, with half an hour being police procedural and the second half being a legal drama. CSI and its spin-offs would frequently bundle the CSI field workers as investigators for storytelling purposes (in the original show, most of the cast were not detectives and did not interrogate witnesses. Jim Brass was specifically the detective who affected the arrests, often having the CSIs explain the science. The show also never got to the trial phase, and in some cases, what if any crime was committed is never stated, as the story focused on getting to &quot;how and why something happened&quot; not the legal ramifications. In one episode, Grissom explicitly tells someone he doesn't have enough evidence to prove the fraud in criminal court... but the insurance companies will see his report and it's enough that they would be able to refuse to pay. In shows that are not explicitly legal procedurals, it might be that the cast of characters is not sufficient to cast for all the witnesses AND/Or the characters are not in professions where they would know how to properly run a court. For example, in one episode of the Brady Bunch, the Brady kids, all of them are High School age or less, hold an ad hoc trial with Alice (the family's maid) as the judge. The case descends into childish bickering and Alice calls a recess when she realizes that her Roast is burning.
Yes to everything. Justified use of force is assault / battery / homicide (as appropriate). "Assault" means that a person has placed someone in fear of their life or person. "Battery" means that a person has physically struck someone in some way. "Homicide" means that a person has killed another human. None of these definitions speak to the legality of the action. You are right about the example being assault. Justified use of force is de facto legal. Assault, battery, and homicide are normally crimes, but the justifications for using force carve out exceptions. If the circumstances fit within the justification, the person using the justified force has not committed a crime. (Generally speaking, the person targeted by said force has.) If the situation you describe fits within the laws of justification within the state (and to be fair, it probably does), then your co-worker is right about the actions being perfectly legal. Police are picky about what they investigate, and prosecutors are picky about what they charge. If it's 100% clear from the evidence that you were justified in your use of force, prosecutors will (typically) not press charges, and so police will not bother with an arrest or further investigation. It's really not worth the time and effort for a case that has 0% chance of producing a conviction. However, if the police and prosecutors have some doubts (e.g., they think your force was excessive and therefor not justified), they can still press charges. Being charged with a crime does not mean you have committed a crime. And vice-versa. Justification is an affirmative defense against charges of assault / battery / homicide. An affirmative defense does not mean "I confess to the crime but have a really good excuse." It means that you admit to certain facts that would normally be beneficial to the prosecution, but claim additional facts that either mitigate or make you innocent of the given charges. In the case of justified force, you are admitting to the action of assault, but claiming innocence. When making your defense, your theory of defense must be internally consistent. You cannot admit to a fact when convenient and deny it when it is inconvenient. "I was in Santa Fe at the time, and anyway, Sam did it," is an example of a self-consistent theory that gives multiple reasons to acquit. That's good, because the jury only needs one reason that gives them pause, and now you've got two chances at that. "I was in Santa Fe at the time, and anyway, he was threatening my life," is not internally consistent. If you argue justification, you explicitly declaim any alibi. This situation is more dangerous, because your defense rests entirely on the credibility of the justification. But if you argue an alibi, you implicitly declaim any justification. So building your defense on things the prosecution can disprove is much worse than taking an affirmative defense of justification.
Yes and no. Using deception to get someone to open the door so that you can execute a warrant is okay (United States v. Contreras-Ceballos, 999 F.2d 432). Leading a criminal to believe that you are a crime-customer (e.g. for purposes of a drug sale) and not a police officer is okay (Lewis v. United States, 385 U.S. 206), but must be limited to the purposes contemplated by the suspect and cannot turn into a general search. Lying about whether you have a warrant is not okay (Bumper v. North Carolina, 391 U.S. 543, Hadley v. Williams, 368 F.3d 747), nor is it okay to lie about the scope of a warrant (United States v. Dichiarinte, 445 F.2d 126). Misrepresenting the true purpose of entry, even when the person is identified as a government agent, negates consent (US v. Bosse, 898 F. 2d 113; United States v. Phillips, 497 F.2d 1131; United States v. Tweel, 550 F.2d 297). However, there is no requirement to be fully forthright (US v. Briley, 726 F.2d 1301) so you can gain entry saying that you "have a matter to discuss with X" even when the intent is to arrest X. In a case similar to what you describe, United States v. Wei Seng Phua, 100 F.Supp.3d 1040, FBI agents disrupted internet access and then posed as repairmen to gain access to the computer. Their efforts were wasted, as fruits of the poisonous tree.
The standard of proof for a criminal conviction is the same. So they would similarly need to prove beyond a reasonable doubt to convict the foreign national of a crime. But deportation is not a criminal proceeding, and has a different standard of proof. (In deportation you also don't have criminal defendant rights like right to an attorney if you can't afford one.) I believe the standard is "clear and convincing evidence".
Anyone can be arrested, as long as the police (and in some cases, anyone) have probable cause to do so. This generally includes two points: You are in the process of committing a criminal act The police have probable cause, generally through evidence, that you are in the process of, about to, or have committed a criminal act. This usually requires obtaining a warrant for the arrest. However, it's important not to conflate searches with arrest. Arrests are when you are being taken into custody for the reasons mentioned above. Searches are when your personal belongings (i.e. property), are searched to collect evidence. It is not up to police to convict someone. This is the job of the judicial system. There's a bit of terminology here: convictions basically mean being found guilty of an offence. Police don't have the ability to convict someone of an offence. They do have the ability to arrest, and charge with an offence. To charge someone with a crime basically means to accuse them of having done something. Now let's get to the actual crime. Since you haven't mentioned a specific jurisdiction, I'm going to use Canadian cases and law, but in general, it should apply worldwide. If the police have reason to believe that you are engaging in unlawful hacking-related behaviour, then they have the authority to arrest you. They simply need to have a reasonable belief that you are engaged in the crime. Something such as connecting you with an IP address and connecting that you were online at the time is enough. If the police need to find out more information (which they generally do, to investigate further into the matter) - they can obtain a search warrant afterwards. With this, they can legally search into your computer, and investigate. Any evidence that they collect can be used in court. I've recently done some research into cyber crimes. One rather infamous case involved the attack on multiple large scale websites, including Dell, Yahoo, and Amazon, in 2000. This sparked a large scale investigations, between the RCMP (Royal Canadian Mounted Police) and the FBI. The attacks were claimed by some to cause nearly 1.7 billion dollars of damage. The hacker was charged with 58 different offences. You can imply from the linked article that he was arrested before his computer was searched.
I'd imagine that testimony from the defendant is rare enough that in the majority of cases, prosecutors do not meaningfully prepare for a cross examination. To the extent they do, I'd expect the preparation is similar to that for basically any other witness. So I wouldn't expect complicated flowcharts, because the general rule at trial is that you only ask questions whose answers are both known and helpful. So if I need to place the defendant at the OK Corral at 3 p.m., I'm only going to ask him where he was at 3 p.m. if I have evidence showing that fact is true -- maybe he gave a written statement to the sheriff, maybe he posed for a daguerrotype, whatever. I expect him to deny it, so I don't ask the question unless I have evidence more convincing than his denial. In this way, a defendant -- like any hostile witness -- is used less to provide any facts of their own, but rather as an involuntary narrator of my own story, authenticating evidence and validating the facts consistent with my theory of the case.
What are the ethical rules that limit interaction between civil and criminal proceedings on the same facts? A private lawyer's job is to look out for the client's interests before the public interest in these cases. In many states, a private lawyer is not permitted to threaten to seek a criminal prosecution to gain an advantage in a civil action. A private lawyer, myself included, will often deliberately not pursue criminal charges in order to not impair the ability of a client to collect a judgment. A prosecutor has wide discretion to prosecute or not when the prosecutor is aware of a crime that there is probable cause to believe was committed. A complaint by the victim is not required in the U.S., but most prosecutors consider a victim's wishes. A prosecutor may ethically make prosecution dependent upon making a victim whole. So is this conflict and result just an "unfair" fact of all common-law justice? What is "fair" is beyond the scope of Law.SE which deals in "what is", not in what is "fair". Or are there mechanisms that exist to satisfy the demands of justice despite this conflict? Not really. Just the good judgment of the individual actors in the system given their respective duties and roles.
If the victim is unable to prove who the culprit was, then it will be impossible to prosecute that person criminally or sue them for civil damages. Incidents like these are rarely enough to cause a police department to throw sufficient investigative resources at it to crack the case without some reason to believe that it is part of something bigger. An unfortunate fact of life is that most perpetrators of crimes and torts get away with it and are not caught. And, if the only available witness is willing to lie to cover up the name of the guilty party (probably out of a desire to not have the dog put down), it is that much harder. A private investigator might be able to solve the case, but the cost of hiring a PI would probably exceed the benefit that could be obtained if the PI was successful.