Veracity judgements are important in legal and investigative contexts. However, people are poor judges of deception, often relying on incorrect behavioural cues when these may reflect the situation more than the sender's internal state. We investigated one such situational factor relevant to forensic contexts: handcuffing suspects. Judges—police officers (n = 23) and laypersons (n = 83)—assessed recordings of suspects, providing truthful and deceptive responses in an interrogation setting where half were handcuffed. Handcuffing was predicted to undermine efforts to judge veracity by constraining suspects' gesticulation and by priming stereotypes of criminality. It was found that both laypersons and police officers were worse at detecting deception when judging handcuffed suspects compared to non-handcuffed suspects, while not affecting their judgement bias; police officers were also overconfident in their judgements. The findings suggest that handcuffing can negatively impact veracity judgements, highlighting the need for research on situational factors to better inform forensic practice.