Can illegally obtained evidence be used in favor of the defendant in a criminal case?

Question

Regarding US law, my general understanding is that if evidence was obtained in an illegitimate way (e.g. under false pretenses), then it may be inadmissible as evidence to support a conviction in a criminal case. The basic rationale for that is somewhat clear, procedurally limiting the power of the government to punish people for crimes in order to make sure police and prosecution will only use the tools that the law allows for.

However, that kind of rationale doesn't really hold up when a defendant in a criminal case obtains evidence that demonstrates the accusation isn't true, but may have been obtained by the defendant in some illegitimate way - if the point is to restrict the power of the government to punish private persons, then a private person defending themselves against punishment by the government doesn't fall under that. As an example, let's say that in a given jurisdiction you don't have the right to film someone on your property without their consent, but you have hidden cameras on your premises anyway, and then you'd like to use those recordings to defend yourself when they show you did not commit a crime you are being accused of.

TLDR: In a criminal trial, when can evidence in favor of the defendant be thrown out on the grounds that the evidence was obtained illegally/illegitimately? What is the rationale for that?

I'm happy with answers for US law, any commonwealth nation's law, or any European nation's law.

Answer 1

france

In France, illegally obtained evidence is not necessarily inadmissible in a criminal case. There are some limits and nuances and case law evolved a bit under the influence of the ECHR but there is no blanket exclusionary rule, much less anything like a “fruit of the poisonous tree” doctrine. The judge is in principle free to assess the evidentiary value of any piece of evidence and the main standard is whether it helps in establishing the truth.

In particular, the legal system gives more leeway to private people than to agents of the state like a police officer. So there are many cases of illegally obtained recordings that ended up being admissible as evidence of a crime. In other words, that's possible even for evidence against the defendant (e.g. something brought by the partie civile).

Answer 2

Yes (in most cases)

Disclaimer: I can only speak to US (Federal and State) law.

There are important differences in how illegally obtained evidence is treated depending on whether it's offered by the prosecution or defense:

For prosecution evidence: The "exclusionary rule" in generally prevents the state from using illegally obtained evidence. This stems from the Fourth Amendment and exists to deter police misconduct. There are exceptions (good faith exception, inevitable discovery, etc.) Click here and scroll to "Exceptions" for more exceptions to the exclusionary rule.

For defense evidence: The key principle that comes into play is the constitutional right to present a complete defense. Courts generally weigh two competing interests:

1. The defendant's right to present exculpatory evidence
2. The public interest in deterring illegal conduct

The general approach in most jurisdictions is:

• Courts are much more lenient about allowing illegally obtained defense evidence compared to prosecution evidence
• The constitutional right to present a defense often outweighs the interest in excluding illegal evidence

However, there are limits—particularly if: the illegal act used to obtain the evidence was especially egregious, and the evidence could have been obtained through legal means, or the probative value is outweighed by prejudicial effect

In your specific example about illegal surveillance footage, this would likely be admissible in most jurisdictions if it clearly showed the defendant's innocence. The defendant's right to defend against criminal charges would typically outweigh the privacy violation. Regardless of the admissibility of the evidence, the defendant might still face separate civil or criminal liability for the illegal recording.

The rationale for sometimes excluding defense evidence:

1. Deterring private criminal conduct remains a legitimate state interest
2. Allowing illegal evidence could incentivize defendants to commit crimes to create exculpatory evidence
3. The integrity of the justice system requires some limits on both sides

Generally, courts prioritize allowing defendants to present evidence, acknowledging the inherent imbalance between state prosecution and individual defense. The standard for excluding defense evidence is typically much higher than for prosecution evidence.

A note worth adding: In civil cases, the rules are often applied more equally between parties, since the state's power to punish isn't at issue.

Answer 3

"Can illegally obtained evidence be used in favor of the defendant in a criminal case?"

No because illegally obtained evidence is supposed to be prevented/struck. But if it gets in, then the court has been defrauded into allowing it in. But, in general, if somehow it did get in, it means to be used to convict:

And that rationale for that is that it's been unlawfully added to record via fraud upon the court having occurred, which means somehow prosecution managed to get defense to be ignorant (extrinsic fraud upon the court, I presume) and have defense get it in for prosecution's own benefit to convict.

Imagine this:

1. A case for an alleged theft has been put against defense.
2. Defense didn't commit the alleged crime (was never at the scene) but thinks that some facility has video recording evidence to prove-up defense not being guilty.
3. Defense breaks into the said facility and gets video recording evidence of not having committed the offense.
4. Defense asserts in court that defense managed to lawfully acquire the evidence and that it should be admitted into record to disprove any of prosecution's claims of guilt.
5. The judge accepts defense's alleged evidence and admits it into record.

Somehow... somehow defense has been misled to thinking it is a good idea to go about getting that alleged evidence. And that misleading managed to go about prosecution's overall center of gravity being used in such a way to deceive defense into thinking that it would be a good idea to get get that recording, such as to enter it in the case. There are two adversarial parties: Prosecution and defense. And both have an overall center of gravity that each uses to combat each other in court relative to alleged facts. Relative to prosecution's overall center of gravity, prosecution had the overall center of gravity that managed to keep defense deceived into thinking it was worthwhile to get get that alleged evidence of not being guilty. Fact is, though, defense ought to have been more focused on using 5th amendment protections rather than seek to enter ANYTHING into the case: Getting rid of things rather than adding things.

"In a criminal trial, when can evidence in favor of the defendant be thrown out on the grounds that the evidence was obtained illegally/illegitimately? What is the rationale for that?"

There is never evidence in favor of the defendant unless it's part of the grounds to vacate judgment, dismiss the charge, strike from the record, or expunge the case (might be other examples). For such motions, the idea is that "evidence" would be argument(s) in support of the motion.

You're forgetting a basic mechanism relative to the fifth amendment of The Constitution of the United States of America extended via the 14th amendment to the state level: The mechanism that it's on the prosecution to prove the defendant guilty, not for defense to prove its innocence. Defense ought to be seeking to refute (deconstructing and eliminating prosecution's argument, such as through getting rid of the record itself) prosecution rather than defense seeking to make a case for its own innocence.

For defense to seek to enter evidence for itself (to supposed, as defense might think, prove-up innocence) is essentially violating the defendant's 5th amendment right, thus generating incrimination for said defendant.

For any critics of my answer, let's imagine the alleged offense was listed as stealing a recording to prove one's innocence. Think about that for a while. :)

"As an example, let's say that in a given jurisdiction you don't have the right to film someone on your property without their consent, but you have hidden cameras on your premises anyway, and then you'd like to use those recordings to defend yourself when they show you did not commit a crime you are being accused of."

In the State of Illinois, statutory law asserts that hidden cameras aren't supposed to be used, such as in a bathroom (I can't remember what ILCS: I think it's state statutory law, anyway). But a judge might get crooked and allow it in (there is a case law system in place, which contrasts with state law, albeit persons might further push the idea of what state law says meaning the judge made a mistake of law).

If a person seeks to enter those videos from the hidden camera (let's say, specifically from a bathroom), then that person (relative to state law) been deceived into thinking it was a good idea to do such. Granted, people get crooked and enter alleged evidence that ought to never have been admitted (fraud upon the court); but it still happens.

But still, there is the matter of the Fifth Amendment of the Constitution of the United States of America: Prosecution's overall center of gravity was of such a degree to keep you deceived from using it along with your overall center of gravity not being high enough to use it while seeking to refute prosecution's claim of guilt.

Answer 4

Typically, the prosecution will go for the "bigger fish" of the two cases and has the discretion not to charge a defendant with a crime if they so choose. It might be that, if a Peeping Tom was to turn in evidence that a neighbor was killing his wife, the prosecutor could strike a deal with the Tom to not charge him with the crime in exchange for his testimony at trial. The rational is that of the two, the murderer is more of a threat to society than the Tom, and if the Peeping Tom must go unpunished. Nothing in the deal needs to immunize the Tom from any future crimes, and police will certainly be knocking on his door if new crimes in the neighborhood come to light. If a witness is granted immunity from prosecution, they cannot invoke their 5th amendment rights on the witness stand, since everything they testify to is never going to be prosecuted.

Another example is that Bob is on trial for the Murder of Alice. The cornor testifies that Alice died no later than 9:30 pm on the night of the 10th. Bob's defense is that he couldn't have done it, because the 10th was on a Friday and Friday's are "Blackjack and Hookers" night, which typically starts at 8 pm and goes well into Saturday morning. Bob not only does this, but produces pictures of him and the girls playing Black Jack with a date stamp of the 10th and all the Hookers in picture testify that Bob was definately there that night and didn't leave for any gap of time long enough to kill Alice. Now, Bob may have some legal problems stemming from the illegal gambling and the solicitation of prostitution, sure... but they are comparitively minor crimes to murdering a human! Bob may even have an explination that will help catch the real killer (such as the coat with his name and blood were left at the scene, which Bob could realize that he cut himself making snacks for the girls in prep for Black Jack and Hookers night, and his brother Charlie offered to clean the coat for him... which tracks with some of the DNA partially matching Bob's DNA... The prosecution could only prove a case against Charlie if Bob testifies and might offer a deal that they will grant him immunity from prosecution for Black Jack and Hookers night if Bob testifies against his brother. Bob can agree and testify, or Bob can refuse and be charged for his crimes (but not the crime he didn't commit). The evidence against Bob entered into the record at his trial for his Friday tradition is now a matter of public record and can be used to link Charlie to Alice without Bob's testimony. The deal is advantageous to Bob because he isn't going to jail on a murder charge and it's advantageous to the prosecution because it means they have to successfully convict Bob before they can even move on Charlie.

In the event that the prosecution discovered the exculpatory evidence through an unconstitutional search and seizure or "Fruit of the Poisonous Tree" (evidence that, while possibley be legally obtained, could only have been done so as a result of evidence obtained by an illegal search) would be barred from introduction by the Prosecution, but not the defendant, since the defendant is not bound by the Constitution (As a general rule, the Bill of Rights are the people's Negative Rights against the Government, which means that the government may not violate those rights unless given permission by the the individual. This comes up in trials from time to time. For example, a defendant may "waive" their right to a trial by jury and instead be granted a bench trial (the Judge alone makes the verdict). One can "waive" their right to Free Speech by not speaking (although U.S. Free Speech Laws are so broad, this is only a technicallity as no speech is a protected form of speech. It's also protected while under oath in that the defendant need not say anything at all and have the presumption of innocence. Or they can waive that by taking the stand and testifying.