Can evidence a person gives to aid an investigation then be used to prosecute that person for an unrelated crime?

Question

Consider the following scenario: a person consents to giving some evidence to aid the investigation or prosecution of a criminal,with the reasonable, good-faith assumption that the use of that evidence will be limited in scope to the particular investigation/trial. That evidence is later used by prosecution against the person who provided the evidence in a separate, unrelated case.

One can easily imagine instances where this occurs:

1. This question is inspired by the recent revelation of some police precincts of archiving DNA evidence collected in one investigation for use in later investigations. The policy in question allowed police to use DNA samples obtained during investigation of rape victims to archive the victim's DNA evidence in databases which were later searched and used to implicate the victims in unrelated crimes. This particular issue has been explored on this site here. ​
2. A person surrenders dashcam footage to a police officer because it contains evidence of a hit and run accident. The footage is later used as evidence against the person because it shows that he or she was speeding earlier that day.
3. Police solicit tips/evidence in the search for a suspect in a violent crime. A person gives an eyewitness account of the crime in a good-faith attempt to aid in the investigation. The eyewitness account implies that the person was in a location and time in violation of their parole, which is later used against them in a separate trial. (edit: I understand that the Exclusionary Rule doesn't generally apply to parole revocation hearings, but the sentiment is the same and one could easily modify the scenario to be about a different secondary crime).

What policies or statutes govern the use of evidence past its original intended use? Does consent to surrender evidence in once case amount to surrendering that evidence for all uses, forever? My prima facie assumption would be that the Exclusionary Rule would apply here because the evidence was obtained in a somewhat disingenuous / coercive manner (good-faith assumption that the evidence was only being provided to aid in investigation of a particular crime) and that such a bait-and-switch collection of evidence amounts to a violation of the 5th Amendment.

Answer 1

There are essentially no such limits on the use of such evidence.

The police are free to use evidence from one case in whatever other cases it may be helpful, and criminals have no right to turn over evidence to the police on the condition that it not be used against them.

The Exclusionary Rule has no application here, because it only governs evidence that was obtained in violation of the Fourth Amendment. Because the defendant here consented to producing the evidence, the Fourth Amendment does not apply.

Nor does the Fifth Amendment prohibit the use of this evidence. The right against self-incrimination only applies to compelled self-incrimination; if a defendant wants to voluntarily confess or turn over inculpatory evidence, he is free to do so.

Answer 2

In general, there is no right under the US Constitution not to have evidence that has been voluntarily provided for another purpose used for further criminal investigation.

The premise of the question is that the evidence was turned over:

with the reasonable, good-faith assumption that the use of that evidence will be limited in scope to the particular investigation/trial.

But such an assumption is not reasonable, and the courts will not honor it, because it is an incorrect understanding of the law. Unless there was a specific written promise limiting the use of the evidence, or a specific policy imposing such limits at the time of collection, the evidence can be used in future unrelated proceedings.

In general, if a person gives unforced consent to a search or an examination of evidence, that person has waived any Fourth or Fifth Amendment rights, the search or examination is lawful, as is any evidence resulting directly or indirectly from it.

Some limited exceptions:

1. Grant of Immunity When a person is put under oath and asked questions, and refuses to answer based on that person's right not to self-incriminate under the US Fifth amendment, and is then given a grant of immunity, the grant will bar the future use of that testimony against the person giving it, within the limits of the grant. The exact limits and what if any future use may be made of the testimony is defined by the terms of the grant of immunity, and may vary a bit.

2. Civil fingerprint images When a person provides fingerprints in certain non-criminal circumstances, including as part of a professional licensing process, as part of approval for th4e adoption of a child, as part of approval for the person to work with children, or as part of a background check for access to classified information, then the fingerprint data is stored in a separate "civil" database and is not subject to random or general check (that is, non-probable-cause-based checks). See this answer for more on this.

As to the specific situations mentioned in the question:

1. Rape Kit DNA There is no federal constitutional right under current case law to exclude such evidence, nor does there seem to be any current state law in any US state requiring such exclusion. There might be local policies not to record such info in a database or retain it beyond the need for elimination. Something like the "civil ID database" solution could be devised, but does not seem to have been implemented as yet, although there are policy arguments for doing so.
2. Dashcam video I question the likelihood of this being reviewed for a speeding infraction. It would indeed require some significant technical analysis to accurately determine the speed at which the car was traveling, unless the video also showed the car's speedometer. However, if the video showed a more serious and clearer offense, such as the driver involved in a hit&run accident, the video would probably be admissible unless there had been an explicit limitation of consent, accepted in writing by the law enforcement officer who accepted the video.
3. Parole violation I suspect that, in practice, the parolee would get a warning, rather than a revocation hearing, because law enforcement generally would like to encourage parolees to report crimes, rather than to conceal them. But I am fairly sure this is a matter of individual discretion, not of mandatory policy or state statute. The relevant officials could proceed with revocation if they thought it a good idea. If the parolee's lawyer at a hearing brought out the circumstances, the hearing officer might take that into account and not revoke the parole.

Answer 3

Yes. A rather well known example: Mark Whitacre was an executive at ADM (Archer Daniels Midland). He turns into a whistle blower about a price fixing scheme around lycine (a livestock feed additive)

However the while this was happening, Whitacre was embezzling millions of dollars. The FBI was able to figure out his crime, in part, from Whitacre's evidence.

There were enough twists and turns in this story that it was made into a movie (The Informant!, https://en.m.wikipedia.org/wiki/The_Informant!) that followed the facts of the story pretty closely.