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Prosecutors must typically share all their evidence–both good and bad–with a criminal defendant. (See my previous blog post for more information regarding what evidence a prosecutor must disclose prior to a criminal trial.)

However, a criminal defendant has far fewer obligations when it comes to sharing evidence with the opposing side. Generally, a defendant must provide the prosecution with only the evidence that he intends to use at trial.

According to Massachusetts Rules of Criminal Procedure 14(a)(1)(B)

Following the Commonwealth’s delivery of all discovery…or court order…the defendant shall disclose to the prosecution and permit the Commonwealth to discover, inspect, and copy any material and relevant evidence discoverable…which the defendant intends to offer at trial, including the names, addresses, dates of birth, and statements of those persons whom the defendant intends to call as witnesses at trial.

This includes, but is not limited to,

  • expert opinions
  • reports
  • tangible evidence
  • exhibits
  • witness statements

Such evidence is referred to as “reciprocal evidence” and it must be disclosed to the prosecution, most often in the pretrial conference report.

It’s important to understand that the defendant is not required to hand over evidence that is damaging to his case–unless, for some reason, the defendant intends to use that evidence at trial. Otherwise, the constitutional right against self-incrimination typically allows the defendant to withhold such evidence from the state.