Can illegally obtained evidence be used to impeach a defendant's credibility at trial?

In the context of criminal procedure, the use of evidence obtained through illegal means, such as in violation of the Fourth Amendment's protections against unreasonable searches and seizures, generally cannot be used in the prosecution's case-in-chief to prove guilt. However, the law does permit the use of such evidence for impeaching a defendant’s credibility if they choose to testify at trial.

When a defendant takes the stand, they are subject to the typical rules of cross-examination. If a defendant's prior illegal conduct or other questionable behavior comes to light during their testimony, the prosecution can use this evidence to challenge the defendant's credibility. This serves to ensure that the jury receives a complete picture of the witness's reliability.

This approach is aligned with the principle that while the integrity of judicial proceedings is paramount and requires exclusion of illegally obtained evidence in proving guilt, the need for truth in the courtroom when a witness—such as the defendant—voluntarily offers their testimony holds significant importance. Therefore, the option of allowing such evidence for impeachment purposes is consistent with balancing the rights of the accused with the pursuit of an accurate and honest judicial process.

The other options, which suggest absolute rules against or conditional usage of illegally obtained evidence (for instance, restricting it only to