Obtaining reference material in a case with two unknown speakers: getting two suspects on speaking terms

Abstract

The case reported below involves the verification of the identity of two speakers who made a number of intercepted telephone calls with one another. Two men, one Dutch and one Irish, were suspected of making the calls, which they denied. At the request of the defence a Dutch Court of Appeal commissioned the Netherlands Forensic Institute (NFI), the forensic science laboratory of the Dutch Ministry of Justice, to conduct a comparative speech examination or voice comparison to determine whether the suspects had been involved in the calls, as the police and the prosecution claimed.