Criminal Evidence Law | Suppression

Estimated reading time: 12 minutes

What is criminal evidence? Evidence is information that either tends to or fails to, prove or disprove a claim. Evidence law concerns reliability and police lawbreaking. And some rules of evidence are criminal-case specific.

The word evidence can mean different things to different people depending upon context and usage. Evidence could mean different things to:

1. a scientist or philosopher.
2. police & private investigators: anything that could prove or disprove a theory.
3. a lawyer or judge: things or information legally admissible in court.

When we speak of evidence in a trial, we mean legally admissible evidence. Admissible evidence is information that passes legal tests meant to increase reliability, fairness, and deter illegal government behavior.

Problems of proof: Lawyers, whether defense attorneys or prosecuting attorneys, have many problems — and some of them we call “problems of proof.” What does that term refer to? Imagine you are sure that something is true. Great. But how can you prove it, exactly? What evidence can you bring into a jury trial in a criminal courtroom, that will be legally admissible?

The restaurant metaphor: Imagine a restaurant, where the trial jurors come to dine. The restaurant staff must obtain the ingredients, then prepare and serve the meal. Is there a meal at all to be served? Does it meet the required level of excellence required by the diners? (The lawyers are metaphorically the cook and wait staff. Jurors are the diners.)

Lack of proof

If criminal evidence is low quality, a wrong may result. In computer science, the descriptive term “garbage in, garbage out” (GIGO) fits here. We’ve all thought something true, having some evidence. And then later we realize we were mistaken. Fortunately in our normal lives, usually no irreversible, permanent harm results.

“It often happens, that if a Lie be believ’d only for an Hour, it has done its Work, and there is no farther occasion for it. Falsehood flies, and the Truth comes limping after it; so that when Men come to be undeceiv’d, it is too late; the Jest is over, and the Tale has had its Effect.”

Jonathan Swift, 1710, The Examiner, No. 15

But in a jury trial, mistakes destroy lives and destroy families. And ultimately, false verdicts have a destructive effect on Society at large and all of us. As a result, the laws and rules of evidence are more strict for criminal prosecutions.

Conservative criminal evidence law

Criminal law is more conservative than general evidence law. For example, consider “the rule against hearsay.” It limits use of “out of court statements offered for the truth of the matter asserted.” This includes anecdotes, rumor, lack of personal knowledge. If a sworn witness testifies in court, “the other witness told me …” that would normally be inadmissible hearsay — in both civil and criminal evidence law.

The constitutional right to confront witnesses against you, however, applies only to criminal cases. A question asked of a witness that calls for hearsay, could also violate the accused’s right to confrontation. But that can only happen in a criminal case. Even when testimony is within an exception to the rule against hearsay, the judge may still exclude it to protect the accused person’s right to confront the source of the statement.

Exculpatory evidence

Investigatory evidence that supports a possible inference of innocence is exculpatory evidence. Police do most of the criminal investigation. But police have an agenda. So it’s important to remember that the defendant has a Constitutional right to potentially exculpatory evidence found.

The government should not hide the truth from the accused, no matter how inconvenient the truth may be. And at trial, the defendant has the Constitutional right to get exculpatory evidence into the record before the jury.

What is exculpatory may be in the eye of the beholder. Yet whether information is exculpatory must be from the defendant’s point of view.

Direct vs. circumstantial evidence

Evidence can be direct or circumstantial. Direct evidence supports a claim directly. It does not rely upon an inference or additional evidence to relate to the claim asserted.

“Circumstantial evidence is a very tricky thing. It may seem to point very straight to one thing, but if you shift your own point of view a little, you may find it pointing in an equally uncompromising manner to something entirely different.”

Arthur Conan Doyle, The Adventures of Sherlock Holmes

Circumstantial evidence refers to a circumstance that could support one of several inferences, only one of them being the asserted claim. Consider this example. You walk outside your front door early in the morning. You see water on the grass. Does this circumstance prove that it had been raining? Beyond a reasonable doubt?

Where circumstantial evidence gives rise to more than one inference, and supports an inference other than guilt; then in a criminal case the court and the jury must conclude that evidence fails to prove a “guilty” verdict. See, State v. Harris, 895 NW2d 592 (Minn Supreme Court 2017). See also, State v. Johnson, 217 NW 683 (Minn Supreme Court 1928); State v. Al-Naseer, 788 NW2d 469 (Minn Supreme Court 2010).

A circumstantial evidence case is the only case at trial in which every witness can tell the truth, and an innocent person can be convicted.

And that is why the government must prove that the only reasonable inference from the facts is guilt. If one can find a real possibility of innocence under the undisputed facts of the case, the verdict must be not-guilty.

“An important body of psychological research undermines the lay intuition that confident memories of salient experiences … are accurate … [T]he mere fact that we remember something with great confidence is not a powerful warrant for thinking it true… [A]ccuracy of recollection is not highly correlated with the recollector’s confidence.”

Krist v Eli Lilly Co, 897 F2d 293, 296 (7th Cir. 1990) (addressing the reliability of memory)

Direct evidence can be unreliable too

Eyewitness testimony and confessions are two categories of types of criminal evidence that we can characterize as direct. That’s because they may not depend upon some other evidence or an inference to directly relate to the dispute.

The law has been aware of the problem of unreliable confessions for thousands of years. Confessions under torture or coercion have been inadmissible due to unreliability, historically and now.

Similarly, eyewitnesses have given false testimony in countless trials and proceedings over the years, and usually not intentionally. The eyewitness often actually believes their own false testimony. And that makes it difficult for juries and other fact-finders who may only be looking for signs of knowing deception.

Modern scientists have also discovered many ways witnesses can be wrong. These include misidentification due to perception errors, to memory and reporting errors.

Is Witness Testimony Evidence?

Yes. In fact the most common type of evidence in a trial is witness testimony. And today in Minnesota, some cases are nothing more than “he said, she said” cases, without corroborating evidence.

The most powerful tool to expose a witness’s testimony, is cross-examination. The right to cross-examine witnesses against you is so vital, that it is protected in the Constitution’s Sixth Amendment:

“In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence.”

U.S. Constitution, Sixth Amendment

Trial lawyers work hard to prepare an effective cross-examination of opposing witnesses. And if the witness gives the wrong answer, we can impeach them with other evidence undermining their claims.

Another important issue with witness testimony is bias. Is the witness a neutral reporter of perceived historical fact? Or, does the witness appear to be pushing an agenda? A common agenda is self-interest.

“The famous Lucius Cassius, whom the Roman people used to regard as a very honest and wise judge, was in the habit of asking, time and again, ‘To whose benefit?'”

Marcus Tullius Cicero, speech in Pro Roscio Amerino, 80 BC “Cui bono?”

Confessions, Statements & Hearsay

A common type of evidence in a trial is testimony about someone’s confession, or statement. Confessions are powerful because most assume that a person would never admit something against self-interest unless true. Upon deeper reflection, however, we know that people often do “confess” to things they did not do. And thanks to the newer technology of DNA evidence, we now know that many people have been falsely convicted for crimes they did not do, based on false confessions. (Approximately 25% of wrongful convictions cases were based on wrongful convictions.) So confessions are not as reliable as we tend to assume.

And in police investigations, police pressure people to admit (confirm) what the police suspect. To make matters worse, some people are particularly vulnerable to making unreliable statements. These include a drunk, a person in a psychotic episode, with a head injury, a child, inexperience with police, and so on.

“An innocent man, when placed by circumstances in a condition of suspicion and danger, may resort to deception in the hope of avoiding the force of such proofs.”

Justice Edward Douglass White, HICKORY v. US, 160 US 408 (US Supreme Court 1896)

Suppression of unreliable, illegal statements

Over the millennia-long development of the law, the law addressed the unreliability of involuntary confessions and statements.

And, the law more recently developed remedies to solve problems associated with confessions and police overreach; including the suppression of statements made in violation of Miranda rights.

“This and no other is the root from which a tyrant springs; when he first appears above ground he is a protector.”

Plato, The Republic, Book VIII, 360 BC

Confronting hearsay at trial

Hearsay is an out-of-court statement a party offers to prove the truth of the matter the statement asserts. (“Out-of-court statement offered for the-truth-of-the-matter-asserted.) Under court rules of evidence hearsay is generally inadmissible — it can’t come into trial evidence, generally because it’s unreliable. Some hearsay is multiple hearsay. In other words, it’s layers of hearsay within hearsay: “He said that he heard the woman there say ….” and so on.

The rules of evidence include exceptions to the Rule Against Hearsay, often based upon the assumption of sufficient reliability for those exceptions. See, e.g., Rule 807, Minnesota Rules of Evidence (residual exception).

But in criminal evidence law, the accused has the Right to Confront Witnesses in court. And even if admissible as an exception to the rule against hearsay; a judge can still exclude it as a Confrontation Clause violation in a criminal case.

“If the Government becomes a lawbreaker, it breeds contempt for law; it invites every man to become a law unto himself; it invites anarchy.”

Justice Brandeis, Olmstead v. United States, 277 US 438 (US Supreme Court 1928)

Suppression of Illegal Evidence

Government run amok: We must force the government to obey the laws, since the government has so much power over all of us. If criminal evidence is from illegal government activity, a good defense lawyer will ask a judge to suppress.

Examples include evidence obtained following an:

Illegal traffic stop or Fourth Amendment seizure;

an illegally prolonged detention;

Unlawful Arrest and Illegal Evidence, and

Illegal search.

“Police officers may not ordinarily make searches upon apprehending motorists for simple traffic violations or upon the slightest hint of illegality.”

State v Varnado, 582 NW2d 886, 889 (Minn Supreme Court 1998)

Technology & criminal evidence

With the development of technology, new forms of evidence become available. But it’s not all good news. It may be more of a two-steps forward, one-step back situation.

Consider DNA evidence, for example. Developments in the forensic use of DNA has made it possible to use ever smaller amounts of DNA as samples; even mixed-DNA samples. Great right? But “touch DNA” has increased the risk of sample contamination, making it unreliable as evidence.

Gallagher Criminal Defense won a client’s case where the prosecutor said her DNA was on bags of cocaine totaling one kilo. Then Attorney Thomas Gallagher uncovered that during the search police placed the bag on the client’s dirty laundry, on a table by the washing machine. Result? All charges dismissed, years in prison avoided, no criminal conviction record, an innocent person exonerated.

The Minnesota Supreme Court held in State v. Steeprock, 28 NW3d 417 (Minn Supreme Court 2025), that warrantless collection of a buccal swab from a defendant pursuant to Rule 9.02, subdivision 2 (1) (f), of the Minnesota Rules of Criminal Procedure is an unreasonable search that violates the United States and Minnesota Constitutions. So, Defendants should refuse to consent to providing a DNA sample, prior to at least consulting their defense attorney. And so courts will suppress evidence resulting from an illegal search of DNA.

Other common types of evidence involving technology include: video and audio recordings, computer, hard drive, cell phone and electronically stored data, data on the web, Automated license plate readers (ALPRs) including Flock cameras, facial recognition, cell tower, and meta tags.

“The true character of liberty is independence, maintained by force.”

Voltaire

Criminal Evidence Law

Where does evidence law come from? Like all human laws, people develop the laws of evidence over time. Experience, trial and error inform contemporary efforts to develop the laws to solve its problems. The main legal authorities for law of criminal evidence are:

• the Court Rules of Evidence and
  
• Rules of Criminal Procedure;
  
• in state and federal statutes and constitutions; as well as
  
• state and federal case-law.

For example, the corroboration rule dates back thousands of years. It requires independent corroboration of a witness’s accusation before a person can possibly be guilty of a crime.

Standards of Proof: criminal evidence

Scintilla of Evidence: The law has different standards, or levels, of proof required for various legal purposes. In civil cases we have the “Scintilla of Evidence” standard. So, a motion for summary judgment will not be granted if there is even the slightest amount of relevant evidence supporting the claim.

Preponderance of evidence: In most civil cases, the party seeking the court’s remedy has the burden of presenting evidence. The preponderance of evidence standard means the evidence must make their claim more likely than not true.

Clear and convincing: In some civil cases, the plaintiff must present evidence that is “clear and convincing” proof that their claim is true.

Beyond a reasonable doubt: But the law reserves its most strict standard of proof for criminal cases. The prosecuting attorney must present enough evidence to eliminate all doubts. The jury presumes the defendant innocent. The prosecutor must try to overcome that presumption of innocence. We can ignore unreasonable doubts, of course.

Just about every juror Thomas Gallagher has met so far has been reasonable, and not prone to unreasonable doubts. If you have a doubt, it’s reasonable.

Right to present defense evidence

Every person facing prosecution by the government has the Constitutional right to present a complete defense at trial. See:

Right to Present a Complete Defense at Trial.

We sometimes see prosecutors’ “Motions In Limine” to exclude defense evidence. But if a trial judge goes along with that, excluding defense evidence can be reversible error, upon appeal to a higher court.

“If a judge’s evidentiary rulings infringe on a criminal defendant’s right to present a complete defense at trial, they violate due process and are reversible error.”

State v. Thompson, 617 NW2d 609 (Minn Court of Appeals 2000)

Defense perspective on criminal evidence

Defense Attorney Thomas Gallagher begins by mapping the known universe of possibly case-relevant information, including investigation and pretrial discovery. Then we evaluate the problems of proof related to that information.

Are there opportunities in the court process, and the rules of evidence, to prevent the prosecution from admitting unreliable, misleading and harmful criminal evidence? Often, there are.

We can ask the judge to suppress unreliable or illegal evidence, in a pretrial motion to suppress. A judge decides these defense motions after a Contested Omnibus Hearing.

Right before the trial begins we can make “motions in limine” to seek court rulings excluding certain criminal evidence based on the rules of evidence and other criminal law. And we can object to improper prosecution evidence during the trial, as well as assert defenses.

Just because you can, doesn’t always mean you should: Sometimes the defense may choose not to object to certain prosecution evidence even though we could, for strategic or tactical reasons.

“In declaring what shall be the supreme law of the land, the constitution itself is first mentioned; and not the laws of the United States generally, but those only which shall be made in pursuance of the constitution, have that rank.

Thus, the particular phraseology of the constitution of the United States confirms and strengthens the principle, supposed to be essential to all written constitutions, that a law repugnant to the constitution is void; and that courts, as well as other departments, are bound by that instrument.”

Chief Justice John Marshall, Marbury v Madison, 5 US 137 (US Supreme Court 1803)

Question? Call Lawyer Thomas Gallagher, 612 333-1500

Minnesota Criminal Defense Attorney Thomas Gallagher is the author of this page. You are welcome to call with your question.

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