This article is a resource for lawyers approaching the cross-examination of forensic scientists (and other expert witnesses). Through a series of examples, it provides information that will assist lawyers to explore the probative value of forensic science evidence, in particular forensic comparison evidence, on the voir dire and at trial. Questions covering a broad range of potential topics and issues, including relevance, the expression of results, codes of conduct, limitations and errors, are supplemented with detailed commentary and references to authoritative reports and research on the validity and reliability of forensic science techniques.