I remember a world before DNA testing. When if a hair was found at a crime scene, about all they could say was what color it was.

Cut to today. How can you get DNA when the suspect might refuse and/or cut and run?

- Do a trash pull (completely legal) and look for dental floss and Q-tips. (Best if they live alone)

- Have a fake market survey, such as a short survey about regional shopping. Go door to door in suspects’ neighborhood, offering to pay them to complete the survey. After they do, tell them that for confidentiality they should be the one to place their survey in an envelope and seal it.

- Bring them in, then turn the heat in the interrogation room to 85 degrees, then offer a bottle of water. Once they've drunk from it, leaving behind their DNA you can say, "I have no idea why they brought you in. You can go."

- If the suspect smokes, have an attractive female agent set up a promo display in shop frequented by the suspect. Ask them to try a couple of cigarette samples and give feedback. Each time, take the half-smoked cigarette back.

- Or try this: tell the suspect you want their opinion on gum flavors.