The same evidence rules apply to both judge and jury trials. Most jurisdictions have only one set of evidence rules, applicable generally to all trials. In practice, however, judges tend to apply evidence rules much less strictly in cases tried before a judge than in those before a jury.
Many judges believe that, unlike a jury, they can sort out admissible and inadmissible evidence when it comes time to decide guilt or innocence. Also, information has to be disclosed to judges before they can decide whether or not it’s admissible. Because they hear about information whether or not it’s admissible, a ruling excluding evidence is less significant in a judge-tried rather than jury-tried case. Sometimes defendants choose judge trials rather than jury trials because they hope that a judge will be subconsciously influenced by information that is technically inadmissible.
Example. Polly Anna is on trial for embezzling funds from the bank where she used to work. She wants to attack the credibility of a key prosecution witness by showing that the witness was previously convicted of a crime. However, because the conviction occurred some years ago and the judge has discretion as to whether to admit evidence of the conviction, Polly’s lawyer is uncertain about its admissibility. This uncertainty might incline Polly toward a judge trial: Even if the judge were to exclude the conviction from evidence, the judge will at least know of the conviction and might be subtly influenced by it. By contrast, if the judge excludes evidence of the conviction in a jury trial, the jury will never hear about it. Of course, a jury trial may nevertheless be the client’s best bet.
Judges often have to hear what witnesses have to say before deciding whether a jury should be permitted to hear the testimony. Evidence that determines the admissibility of other evidence is called “foundational evidence”; the phases of trial involving foundational evidence are often called “minitrials.” In a jury trial, in order to prevent jurors from finding out about evidence that the judge ultimately finds inadmissible, the judge typically excludes the jury from the courtroom during the minitrial.
Example. Miguel Ito is on trial before a jury for burglary. The prosecution wants to offer into evidence a confession he made to a police officer shortly after being arrested. Miguel claims that the confession was taken in violation of the Miranda rule and is therefore inadmissible. The judge will conduct a minitrial. After listening to foundational evidence about the confession and whether the police followed the Miranda rules, the judge will decide whether to admit the confession into evidence. To prevent the jury from learning about the confession unless the judge finds it admissible, the jury will be excused from the courtroom during the minitrial.
Limiting instructions come into play when, as is often the case, evidence is admissible for one purpose but not another. A judge will often instruct (“admonish”) jurors to consider the evidence only for the legitimate purpose, and to ignore it for any other purpose. Following a limiting instruction can require mental dexterity that few people possess.
Example. In an assault case in which the defendant claims self-defense, the alleged victim testifies, “A day before the fight, my brother told me that the defendant had once killed a man.” The judge admits the testimony because it would allow the jury to infer that the victim feared the defendant and therefore didn’t initiate the fight. At the same time, evidence rules forbid the jury from considering the testimony as evidence that the defendant actually had killed a man—that would amount to hearsay and potentially impermissible character evidence. The judge should issue a limiting instruction telling the jurors not to consider the statement as evidence that the defendant actually killed a man. Rather, they should consider it only as evidence potentially showing the alleged victim had a reason to fear the defendant. As you can see, this is tough distinction to make.
If you’re facing criminal charges, you’re almost always best off letting a lawyer represent you. The rules of evidence are tremendously complex and nuanced; only an experienced attorney will be familiar enough with them to provide a competent defense to criminal charges.