Can a vigilante be useful for a police department? (Just for reference, this question is for a story I'm working on, and I wanted a realistic look at the law's side of things.) So, a lot of fiction likes to play off the trope of a Vigilante. This person, (superhero or otherwise) often cuffs the baddies, and leaves them gift wrapped for the police, along with providing damning evidence to go with that. So my question is, does that actually help the police in any way? These situations are almost always portrayed as: Acquiring evidence without a warrant Falsely imprisoning a person/criminal (This does not always involve the Vigilante seeing the crime happen, but they are usually acting like a police officer and pre-empting the crime. The Vigilante is generally unable to be present for the accused to 'face their accuser'. So, if evidence came from a known Vigilante, can it be used in a court of law?
Can a vigilante perform an arrest? This depends on whether the vigilante has the power to perform a citizen's arrest. The rules depend on the jurisdiction (and vary from state to state in the US), but generally the power to perform a citizen's arrest is quite limited. It may include the power to 'pre-empt' an offence if the would-be offender has attempted to commit the offence. However, often the power is limited to particularly serious offences (eg. felonies). There may also be a requirement that the crime occurred in the citizen's presence, or that the citizen was unable to contact the police instead. Is evidence obtained by a vigilante admissible? In the United States, the constitutional exclusionary rule generally prevents evidence from being admitted if the government obtained it illegally. I answered a general question about the scope of the exclusionary rule here. However, the Fourth Amendment exclusionary rule does not apply to evidence obtained illegally by a private individual: Burdeau v. McDowell, 256 U.S. 465 (1921). In Burdeau, the defendant's papers had been stolen and turned over to the government, which proposed to present them as evidence to a grand jury. The Supreme Court said: In the present case, the record clearly shows that no official of the federal government had anything to do with the wrongful seizure of the petitioner's property ... there was no invasion of the security afforded by the Fourth Amendment against unreasonable search and seizure, as whatever wrong was done was the act of individuals in taking the property of another ... We assume that petitioner has an unquestionable right of redress against those who illegally and wrongfully took his private property under the circumstances herein disclosed, but with such remedies we are not now concerned. However, the exclusionary rule in some states goes beyond the Fourth Amendment. For example, article 38.23 of the Texas Code of Criminal Procedure provides that evidence illegally obtained 'by an officer or other person' is inadmissible. This provision was apparently enacted to deter vigilantes: Bubany and Cockerell, 'Excluding Criminal Evidence Texas-Style: Can Private Searches Poison the Fruit?' 12 Texas Tech Law Review 611 (1981), p 625. Can such evidence be admitted even if the vigilante is not present? Assuming that no exclusionary rule applies, evidence obtained by a vigilante can potentially be admitted through the testimony of a police officer or other witness, subject to the rule against hearsay and the question of reliability. The rule against hearsay means that a police officer cannot give evidence that a vigilante told them that the accused was guilty. Evidence of this kind is not admissible because the accused has no opportunity to challenge the reliability of the source of the information in cross-examination. The rule against hearsay does not apply when the probative value of the evidence does not depend on the truth of the absent vigilante's assertion. If the evidence provided by the vigilante is really 'damning' then it might fall into this category. For example, a vigilante might provide the police with a weapon that has the accused and victim's DNA on it, or tell the police that incriminating evidence can be found at a particular location. A police officer can then give evidence that the weapon was tested and found to have matching DNA, or a search warrant was executed and the incriminating evidence was found. There is no admissibility issue here. However, the fact that the police were tipped off by a vigilante who has broken the law and is not present to face court may cause the jury to reject the evidence as unreliable (ie. it could have been planted).
So for your first question, yelling "Stop Thief" loudly at the thief is perfectly legal (Like Yelling "Fire" in a crowded theater, it's legal if the theater is infact, on fire... the quote implied that it was a prankster who drew amusement from the reaction of the people who took him seriously). This may alert store employees, who have a specific kind of Citizens Arrest Power known as "Shopkeeper's Privilege" and is a reduced liability compared to Citizens Arrest. This is also pretty basic self defense agains people who are not engaged in any physical action against you but are starting to scare you. Suddenly shouting draws attention to you and discourages them from their behavior "I SAID DON'T TOUCH ME" being suddenly shouted in a Wal Mart is going to get notices from the immediate crowd drawn to you, and by poximate location, the person who is making you uneasy. For your second question, maybe, it depends... since the cop is clearly chasing the guy, you meet the qualification to use non-deadly force in stopping the criminal (i.e. you are witnessing a person committing a crime, in this case, resisting arrest or persuit) and it would certainly be reasonably non-deadly force if you were to trip, grab, or push the fleeing suspect. Citizens Arrest doesn't specify a minimum time to qualify, so if the officer is seconds behind, and you detain the criminal in this action until the gap is closed, it still counts.
This would be illegal in Australia (Criminal Code Act 1995 part 10.7: any unauthorised impairment of electronic communication to or from a computer), the US (Computer Fraud and Abuse Act) and any other jurisdiction that I can think of. There is no exception allowing vigilante action in case a person has a reasonable belief that the material on a website is offensive or illegal. In general, the law does not allow immunization against criminal prosecution in case the victim of an attack is himself a criminal. Only the government has the right to punish criminals.
In short, no, that cant be a pardon for those police officers who would be now influenced to take more violent actions towards those they detain. Pardons are only applicable to past actions. You may be pardoned before charges are filed, but the actions must have already occured. Though I less certain about this, simply because Ive never heard such a thing proposed, I would also note that it is highly improbable that the actual statement he made - generic and during a speech - could everbe interpreted as an affirmative act intending to grant pardons to anyone who may act in that manner in the future.
In many jurisdictions, there is a "witness fee" that one is required to pay, as a token recognition of the value of a person's time. Fact witnesses can often be obligated to appear and testify, for minimal compensation, but not against themselves. In federal cases, Rule 17(b) of the Rules of Criminal Procedure permit the defendant to apply to ask the government to pay the witness fee if they cannot afford it and the presence of the witness is necessary for an adequate defense. The other side of a case (in this example, the prosecutor) could try to impeach the witness's testimony (i.e. make him seem less credible in the eyes of the jury) by demonstrating that the witness is a "professional witness" (i.e. fees from saying things in court are a major part of the witness's regular income). That doesn't seem to apply to the facts you've listed, where the witness just happened to be in that place and time to observe what happened and (assuming for this question) accurately testified as to what he saw. Personally paying the police officer or judge for a favorable result is a different question with a different answer.
Nothing is typical Investigators have wide discretion on how (and if) they pursue an investigation of an alleged crime. When they make an arrest is part of that discretion. Making an arrest starts all sorts of clocks running on the legal process and investigators may not want to do that for all sorts of legitimate reasons.
In most US States (probably all of them) failure to follow the Lawful orders of a police officer is itself a crime, and is grounds for the officer to arrest the person, even if the person had not done anything wrong prior to that. This obviously leads to the question: what orders are lawful? The officer has a pretty broad range of discretion. Ordering a person out of a car, or to roll down a car window, is pretty clearly lawful. Ordering a person to commit a crime would not be lawful. Neither would ordering a person to submit while the officer rapes or robs the individual be lawful. In practice, the officer will usually think that all of his or her commands are lawful, and might feel threatened by any failure to comply. In which case, the officer might shoot. This might not be upheld later if the command was not lawful and/or the officer's fear was not reasonable, but that will do the person shot little good. It is usually wise to comply with any commend, unless it puts you very directly at serious risk. Remember you don't know what else has happed to the officer that day. Has the officer had a fight with his/her spouse that morning? Just been denied a promotion? Been turned down for a mortgage? None of that should matter, legally, but it will affect the officer's attitude, and can lead to escalation, even if the person stopped is in no way at fault. An instruction to "shut up" is probably not going to provoke an officer to shoot if it is disobeyed, but it might help to escalate the situation. It is probably lawful, depending non the exact circumstances. As to the first amendment issues, that would probably come under the 'time, place, or manner" regulations that may be applied to speech. And even if it is not held to be lawful, the time to contest it is in court, not during the stop. If the officer feels safer with the window fully rolled down so that the officer could reach in, that is probably a lawful command.
The advantages are: police officers, like all enforcement officers, have discretion on how they treat what they perceive to be transgressions of the law they enforce. If you are cooperative and helpful they may exercise that discretion to your benefit, if you are obstructive and difficult they may exercise it to your detriment: this may be the difference between a warning, a ticket and an arrest. one of the things that judges are allowed to take into consideration when sentencing is remorse. While the linked podcast indicates that this is not an easy thing to objectively define, it includes accepting that what you did was wrong and mitigating the harm that was done which would include cooperating with law enforcement. The disadvantages are: you may reveal information that is not known to the officer. This may or may not be admissible evidence but, notwithstanding, it may serve as a basis for further investigations which can discover things you would rather the police officer did not discover. For example Officer: "Do you know why I stopped you?" You: "I assume because of the dead body I have in the boot."