Deceiving suspects about their alibi is equally harmful to the innocent and guilty

A common belief in police officers is that guilty suspects' statements are less consistent than innocent suspects'. This could leave guilty suspects more vulnerable to missing inconsistencies externally induced into their alibis. Source monitoring and cognitive load approaches suggest that untruthfulness rather than guilt should predict proneness to such deception. Manipulating both guilt and truthfulness, we tested these opposing hypotheses. One hundred twenty‐six participants were accused of stealing gift vouchers after wandering about a building. When interviewed several days later, participants rarely detected alterations in their alibi (23–29%). Unexpectedly, for one of three detection measures, untruthful participants detected more manipulations than did truthful participants. Guilt did not moderate detection rates. Manipulations were equally harmful for guilty and innocent suspects, and blindness to the alibi manipulations was not useful for discriminating innocent from guilty suspects. Because blindness effects are easy to elicit in the legal context, techniques that externally induce inconsistencies should be avoided.