Write to the investigating agency asking whether evidence is retained, where it is stored and whether it has been tested.
Sometimes. Property logs, destruction records and lab submission records may be available, though exemptions for open investigations vary by state.
Medical examiners, state crime laboratories, court clerks and any agency that previously handled the case may hold samples or exhibits.
Ask for the destruction record and policy applied, and whether lab notes, photographs, extracts or database profiles from earlier testing survive.
Families can ask in writing; agencies decide based on solvability, cost and lab capacity, sometimes using federal cold case grants.