Witness statements obtained through Article 31 violations face potential exclusion, though analysis differs from suspect interrogations. When military superiors question subordinate witnesses about offenses potentially implicating them, Article 31 applies. Failure to warn witnesses who become suspects during questioning can exclude their statements entirely, not just self-incriminating portions.
The key determination involves when witnesses transformed into suspects requiring warnings. Objective factors include question focus shifting toward witness conduct, investigator suspicion development, or witness admissions raising personal culpability. Retroactive warnings after incriminating admissions don’t cure violations – the cat’s already out of the bag.
Derivative evidence complications arise when improperly obtained witness statements lead to other evidence. If witnesses revealed co-conspirator identities or evidence locations without warnings after becoming suspects, fruit of the poisonous tree doctrine may exclude derivative discoveries. This cascading suppression can devastate cases built on unlawfully obtained witness cooperation.
Defense strategies include scrutinizing all witness interviews for moments when Article 31 should have applied. Many investigators fail to recognize when witnesses become suspects, continuing questioning without warnings. Even if clients weren’t present, challenging unlawfully obtained witness statements can exclude crucial prosecution evidence. The analysis protects witnesses from self-incrimination while ensuring lawful evidence gathering.