There are many rules governing whether or not a particular piece of evidence can be introduced at trial. Often, these rules are applied to prevent the prosecution from introducing evidence. Do the same rules generally also apply to the defense?

For example, suppose officers obtain a DNA sample and send it off for testing. Later, it turns out they needed a warrant, but didn't get one, so the prosecution cannot use the test results. If the test shows the suspect is not the culprit, is the defense allowed to introduce this into evidence? Or are they bound by the same rules as the prosecution?

1 Answer 1


You're referring to the Exclusionary Rule, which bars the government's use of evidence it obtained in a bad-faith violation of the defendant's Fourth Amendment rights. It is typically only applied when a defendant objects to the use of the evidence, so it would not prevent a defendant from using that evidence if he wanted to. The government would not have standing to object to the defendant's use of the evidence.

If a defendant improperly obtained evidence, it could be subject to exclusion, as well, but there would likely be a heightened standard for doing so, given the defendant's Sixth Amendment right to a fair trial.

  • Could the defense change its mind? Can the defendant object, have the evidence dismissed, later realize it is exculpatory, and rescind the objection? Couldn’t the government say, “We realized we had in fact wrongly acquired that evidence. We agree with the earlier ruling that it should be dismissed”?
    – JPM
    Commented Aug 2, 2020 at 19:54
  • After seeking and obtaining a ruling excluding the evidence, it's probably left to the judge's discretion whether to allow it in anyway. I suspect most judges would allow the defense to do so, assuming that it didn't appear that the defense was deliberately trying to bait-and-switch the prosecution.
    – bdb484
    Commented Aug 10, 2020 at 4:13

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