I have argued for many years that the police should make greater use of forensic technology in documenting crime - Rape is a special case, but all crimes have victims. Fingerprinting, palm prints DNA, everything that identifies an individual should be collected, collated in one database and referenced every time someone new is added to the list.
This may not immediately solving a case, but documenting who did it on the basis that sooner or later, like turds, they will float to the surface will produce convictions. Currently crime pays and perpretators will probably get away with it - if people find criminals are being caught at any time, even years after the act, it may reduce crime rates, particularly if deterrent penalties are imposed.