Olivia Martin: CRISPR, a Heat Block and a Piece of Paper

In casework, stains are often invisible, mixed, or of unknown origin, so a useful test must screen for several fluids at once. Current methods force a trade-off.

Rapid chemical tests are cheap and work at the scene, but unreliable: they react to non-target substances such as plant compounds and cleaning products, and each identifies only one fluid. More accurate methods detect RNA markers that are highly expressed in a single fluid and can test several fluids simultaneously, but need expensive laboratory equipment and take 1–2 days. Two recent technologies close this gap.