I Always Feel Like somebody's Watching Me, Part 2.

State v. Athan,  158 P.3d 27, (Wash. 2007).

In this case, a 13 year old girl was murdered and raped in 1982, and dumped in a cardboard box. Athan had been a person of interest because he was known to frequent the area where the girl was abducted from. He was not charged, but a cold case review twenty years later cast an investigative eye on him. 

Detectives created a ruse to get a DNA sample from Athan without alerting him to the reopened investigation because it was determined that he was a flight risk.

What they did was they created a letterhead from a fictitious law firm that was allegedly pursuing a class action lawsuit concerning parking tickets. They sent Athan, now living in New Jersey and a flight risk, a class action authorization with a stamped return envelope. Athan filled out the form and....you guessed it....licked the envelope flap.

The rest is history. He's a guest in a fine Washington correctional facility for the foreseeable future.