I've read that "Everything which is not forbidden is allowed." I don't know if this is strictly true in the USA.

I also saw in another question that the following Colorado law exists for tampering with evidence.

A person commits tampering with physical evidence if, believing that an official proceeding is pending or about to be instituted and acting without legal right or authority, he:

(a) Destroys, mutilates, conceals, removes, or alters physical evidence with intent to impair its verity or availability in the pending or prospective official proceeding;

The "acting without legal right" verbiage confuses me. Don't I have a legal right to do it if it's not illegal? Or is there a difference between having a right to do something and that act being legal?

Wouldn't this Colorado law be meaningless, similar to a USA law saying:

Speaking in public is illegal unless you have the legal right to do so.

  • In NYC, the correct saying is "everything which is not forbidden is mandatory" Commented Oct 15, 2021 at 15:26
  • 2
    @ReinstateMonica Quantum physics uses this formulation extensively.
    – fraxinus
    Commented Oct 16, 2021 at 12:25

3 Answers 3


It's generally correct in the American system that everything not forbidden is permitted.

But the law you're looking at isn't really an exception. You have the legal right to tamper with evidence if tampering is not illegal, but this statute makes it illegal.

The language you've highlighted merely says that the law does not apply to those who have some other affirmative grant of authority to do so. So if you stab someone to death in your kitchen, you can't remove the body or other evidence, but the detectives investigating the case can, because they have the legal authority to process the scene and maintain the evidence for trial.

So the law is similar to the "speaking in public" hypothetical, but that doesn't make it meaningless. Because of the First Amendment, that law doesn't actually outlaw anything, but the tampering law faces no such legal barriers.

You had the right to tamper until the government said you didn't. Now that it says you don't, you can only do it on the government's terms, which require an affirmative grant of authority.

  • 3
    Your answer is sinking into my skull now. So the Colorado law means "...acting without affirmative legal right or authority..."? Is there no affirmative legal right to dispose of your own property?
    – James
    Commented Oct 14, 2021 at 16:58
  • 8
    Exactly. Tampering is now forbidden, unless the law affirmatively says otherwise.
    – bdb484
    Commented Oct 14, 2021 at 17:01
  • 17
    @James you can deal with your own property as you like. Unless it’s against the law. For example, if that property is no evidence. Or disposing of it breaks environmental law. Or it’s an unregistered motor vehicle and you want to drive on the road. And so on.
    – Dale M
    Commented Oct 14, 2021 at 19:41
  • 3
    you have the right to throw away property, but not the right to do so if it is evidence.
    – Tiger Guy
    Commented Oct 15, 2021 at 0:52
  • 7
    @James In combination it should read as "You have a right to destroy your own property unless that property is evidence, then you don't, unless you have special permission to destroy evidence, then you can again.". Commented Oct 15, 2021 at 18:35

@bdb484's answer is good and correct. I'm coming in with the advantage of its commentary to address the questions generated there; this is just too long for a comment.

I own a kitchen knife. I can do with it as I please - carving a turkey for dinner, opening packages, throwing it at a dart board, or throwing it away.

One day, I use that kitchen knife to kill someone. Killing people is illegal (generally). Since I've used the knife to commit a crime, the knife is now physical evidence. If I move the knife, throw it away, melt it down, or possibly even run it through the dishwasher, I've destroyed, mutilated, concealed, removed, or altered physical evidence, almost certainly with the "intent to impair its verity or availability in the pending or prospective official proceeding".

Thus, after I've murdered someone with the knife, I can no longer legally dispose of it (etc.) even though I still own it. The knife is no longer merely property, it is also physical evidence. Since it is now physical evidence, this law comes into play and it's illegal for me to take advantage of the normal rights I have to my property.

The police investigating the murder have the right to remove the knife as a routine part of the investigatory process. Their removal (and any subsequent alterations; eg., removing some of the blood to run tests) would be done without "intent to impair its verity or availability in the pending or prospective official proceeding" - in fact, their removal (etc.) is done with the specific intent to maintain its verity and availability. So, their actions are legal under this law.

So, we've got 2/3 of the law handled: I can't destroy the knife since I would be doing so to impair its availability, and the police can remove the knife from the crime scene because they're doing so without intending to impair its availability. Why, then, does the "acting without legal right or authority" clause exist?

I can see four categories of reasons for the "legal right or authority" clause:

First, as a broad clause that allows "weird" situations to be handled without jumping through too many hoops. Consider a suit that alleges that all of the evidence bags manufactured by Brand X between dates Y and Z were somehow tainted by the manufacturer (see, eg., the Phantom of Heilbronn, where a cotton swab factory's swabs were contaminated leading to police thinking they had a prolific serial killer on their hands) and a judge ordered that all evidence in those bags be destroyed. Lucky for me, my knife was in one of those bags and a police tech of some sort is going to destroy my knife. Are they acting "with intent to impair its verity or availability"? Probably, actually, since the judge's order was to destroy the evidence so that it couldn't be used. But, that doesn't matter: they're acting with the legal right or authority to destroy the evidence, so they're not committing a crime under this law.

Second, to allow evidence lockers to be cleaned up. If I've been found guilty and am out of appeals, is there any value in keeping my knife in an evidence locker somewhere? What if I've died? What if I died 100 years ago? If there are clear and reasonable policies for the destruction of evidence that can no longer be reasonably required, is the person destroying said evidence acting "with intent to impair its verity or availability"? It doesn't matter: they're acting with the legal right or authority to do so.

Third, to handle evidence which is dangerous to collect or store. This could include explosive devices, drugs, etc.. My brother-in-law had a summer job destroying seized pills (alleged prescription drugs) for the local police department (which included a lot of paperwork and cross-sign-offs). Bomb squads intentionally detonate explosive devices. Do those people act "with intent to impair its verity or availability"? Again, it doesn't matter: they've got the legal right and authority to do so.

Fourth, to handle legitimate mistakes by those in custody of the knife. I grant that this is the weakest reason, though. If I've (illegally!) washed the blood off of my knife before the police take it, consider the lab tech who scrapes off the tiny bit that I missed to run various tests on said blood (legal due to no intent to "impair its verity or availability"), then trips and drops the vial with the bit of blood in it. Did they destroy the evidence with the intent to impair its availability? Probably not, but they had the legal right and authority to do what they were doing and the trip was accidental; they shouldn't be guilty of a felony for stumbling in the lab.

Therefore, all three clauses are necessary for the law to have its desired effects:

  • I lose property rights when my knife becomes physical evidence
  • the investigators gain a number of rights to my knife when it becomes physical evidence
  • there are mechanisms by which my knife can still be destroyed or altered with the intent to impair its verity or availability, if appropriate

But, wait, you might say: none of those scenarios should qualify as "with the intent to impair its verity or availability".

There's one more clause to that law which is important to consider:

(b) Knowingly makes, presents, or offers any false or altered physical evidence with intent that it be introduced in the pending or prospective official proceeding.

Consider a "molehunt" or other internal investigation. It may be necessary for false evidence to be introduced to a suspected bad actor, even if the purpose is to see if that evidence is introduced in the official proceeding. Without that "legal right or authority" clause, such an internal investigation may be functionally impossible to conduct. For example, if there's suspicion that a prosecutor is, shall we say, "less than ethical" with regards to where they get their supporting evidence, it may be necessary to provide them with false evidence to prove their wrongdoing when they use that evidence in court. In that case, whoever made and presented the false evidence would be acting with the legal right or authority to do so, so would not be guilty of a felony under this law.


As my (income) tax professor said (about taxation), "you often have a general rule, an exception to the rule, and an exception to the exception."

The general rule is that you can "tamper" with the evidence to a deed. (You can clean up after yourself.)

The exception to the foregoing is that you may NOT "tamper" if 1) the deed in question is criminal, and 2) you have reason to believe that the authorities will soon want to look into it. (You must wait for a "reasonable" period of time before "tampering.")

Nonetheless, if you are a properly constituted authority with the legal right to do this (policemen or detective), you may do with evidence anything the law allows: mark it, transport it, dispose of it, etc. after you have finished "investigating" it.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .