Can officials enjoy immunity for any crime by asserting they acted in official capacity? Government officials in the United States enjoy broad immunity from personal and criminal liability for "official" actions. However, even the sitting U.S. President is not immune to being tried for crimes committed "unofficially". Yet I can imagine an official making a colorable argument that any action was performed in an "official" capacity – especially when that official is the government's chief executive. Take an extreme hypothetical: The President murders someone in cold blood. Rather than evade detection for the crime, and rather than raising traditional defenses at trial, he simply declares, "I killed that person in my official capacity." After all, the President orders extra-judicial killings all the time. Take the hypothetical down the line to beat police officers, who (as a whole) often kill people in their official capacity, and who claim they are "never off-duty." What laws determine how claims of immunity for "acting in official capacity" should be adjudicated?
There are two kinds of immunity: absolute and qualified. Absolute immunity is limited to the official discretionary acts of judges, prosecutors in the litigation process (but not in the investigatory process) and the President. And, in the cases of judges and prosecutors this is only immunity from civil liability and not criminal liability. Thus, for judges the scope of absolute immunity extends to legal rulings and conduct related to being a judge in a courtroom. In the case of a prosecutor, it pertains to litigation conduct (but not conduct physically dealing with a defendant or investigating a crime). This is usually an open and shut question which can be determined on the face of the legal complaint against the official. Only the President has relatively broad kinds of activities covered and his saying he is immune doesn't mean that a judge trying a case will agree with him. If he's murdering his wife, no judge will believe that he's acting in his official capacity to do so. Other government officials generally have only "qualified immunity" which means that they have liability if they intentionally violate clearly established law, which basically means that there is a binding judicial precedent governing the facts and circumstances at issue.
No. It is illegal to hire someone to kill someone else. Even if the killer enjoys diplomatic immunity, the person hiring the killer has committed a crime. As to your last paragraph, that is properly a separate question, but the answer is that they can't do it because murder is illegal.
What exactly would a prosecutor charge? State? Federal? It depends on whether it is a state or federal prosecutor. It appears that the president has at least flirted with violating both federal and state law, in which case he may be charged by both the federal and state prosecutors, each one laying charges under the relevant body of law. Would Trump be vulnerable to Federal prosecution of the phone call after he leaves office? Yes, if the facts support such a prosecution. It's not clear to me that the conversation constituted an unambiguous violation of the federal statute, but I have no knowledge of any precedent that might inform such a determination.
There is a general defence to any crime called self defense. If you commit a crime, but the reason you commit it is because you are acting in self defense, or the defense of another, then you will not be found guilty of that crime. For example, if you kill someone, but the court believes you are acting in self defense, then you will not be found guilty of murder (or manslaughter). This defense extends to other crimes too, and trespassing would be included in this. Acting in the defense of another person has the same effect as acting in self defense. Just note that you would have to prove that it was reasonable for you to be acting in the way you did. Usually this means that the crime you committed was proportional or necessary to prevent the crime that would have occurred, and if self defense is involved, that it was necessary to do what you had to do to prevent harm to you or another.
The answer provided by Dale M is half right, but there are a few things that I think are wrong. Firstly, the actual reality of the situation doesn't matter. What matters is that you act in a reasonable manner, performing assessments of the situation as a reasonable person would do. If you misread the situation, and end up killing a police officer that was acting in a lawful manner, it doesn't necessarily mean you were acting unlawfully yourself. Because police officers are generally exposed to situations where they would be forced to use their firearm, that obviously would impact how a reasonable person would see the situation, but the test for reasonableness would not go out the window. In addition, even if you were found to not be acting in a reasonable manner, there is certainly a question if you would be found guilty of a lesser charge of manslaughter rather than murder. It's possible the self-defence claim would be upheld as an imperfect defence.
The President has the power under Article II of the U.S. Constitution to faithfully execute the laws enacted by Congress. Any power that the President has to regulate international travel of non-U.S. citizens arises from statutes enacted by Congress that give the President (or the executive branch more generally) that authority. Immigration laws, in practice, give very substantial discretionary authority to the President, and public health laws probably also do so. I don't have chapter and verse to cite to you regarding which specific statutes provide that authority, without considerably more research, but that is the general idea. The primary statute regulating immigration is the Immigration and Nationality Act of 1965 (and more generally, Title 8 of the United States Code). It is not uncommon in the United States for there to be disputes over how much discretion a President has under a particular statute in the United States, because unlike parliamentary systems of government, the execution of laws and the passage of law is split between different branches of the federal government in the Presidential system of the United States, rather than being fused with a Prime Minster who serves at the pleasure of the legislature.
Perjury prosecutions are hard to win, and therefore are not often brought. It is hard to think of a situation in which both &quot;yes&quot; and &quot;no&quot; would be subject to a perjury prosecution. This Justia page says that for statements made under oath, one must prove the following elements to establish a case for perjury: A person took an oath to truthfully testify, declare, depose, or certify, verbally or in writing; The person made a statement that was not true; The person knew the statement to be untrue; The person made the false statement willfully; and The subject matter of the statement was material to the proceeding in which it was made. A US DOJ page on Elements Of Perjury -- Specific Intent says: The third element of a perjury offense is proof of specific intent, that is, that the defendant made the false statement with knowledge of its falsity, rather than as a result of confusion, mistake or faulty memory. United States v. Dunnigan, 507 U.S. 87, 94 (1993). Section 1621 requires that the defendant have acted &quot;willfully&quot;; the section 1623 requirement is to act &quot;knowingly.&quot; In practice, these standards are virtually identical, although the government need not prove both willfulness and knowledge to sustain a section 1623 prosecution. United States v. Fornaro, 894 F.2d 508, 512 (2d Cir. 1990). Under either statute, the government must demonstrate the defendant voluntarily made the false statement with knowledge of its falsity. If the defendant believed his or her statement to be true when it was made, even though it was false, this essential element will not have been proven. Smith could reply &quot;Either 'yes' or 'no' would be a misleading answer. I would prefer to give a more detailed answer. May I do so?&quot; If, after that, the Judge insists on a Yes or No answer (which does happen but none too often) I think it would be very hard indeed to make a case for perjury from the answer. Such a request to expand the answer would make the &quot;willful&quot; element almost impossible to establish. Smith could also ask to consult counsel before giving an answer, and it would be unusual for this to be refused. If Smith had gone though a plea of 5th amendment and immunity process, it is likely that Smith would have consulted a lawyer during the process, and pretty much certain that Smith had a chance to do so.
Diplomatic immunity means that diplomats are immune from prosecution in their host countries. It does not necessarily mean that they can be sued or prosecuted in their home country. Whether the diplomat is subject to the home country's laws and courts is up to the home country. In most cases, it seems, diplomats can escape prosecution altogether by reason of their immunity. If the home country wishes to dissociate itself from the diplomat's actions, it can waive diplomatic immunity to enable prosecution in the host country's courts. There are some interesting examples, some of which touch on your question, in the Wikipedia article on diplomatic immunity. With respect to your example of an apartment lease, it appears that a diplomat might not actually be immune, since the Vienna Convention on Diplomatic Relations of 1961 provides for some exceptions to immunity, including A real action relating to private immovable property situated in the territory of the receiving State, unless he holds it on behalf of the sending State for the purposes of the mission Interestingly, the Wikipedia article lists two prosecutions under home-country legal systems that both involve Romania, and both involve fatal accidents in which the driver had been drinking alcohol. (In one case, Romania was the sending state, and in the other, it was the receiving state.) In one case, the driver was an American Marine assigned to guard the US embassy. He was tried in a court martial, presumably under the US military code, which no doubt penalizes drunk driving, but that's just a guess. The court may well have applied Romanian law. In the other case, Romania apparently prosecuted its chargé d'affaires in Singapore after a fatal automobile accident. It's not clear whether he was charged under the Romanian or Singaporean law.