There is no better sense of gratification than a killer getting caught for his or her crime when a case appears to have very little evidence initially and seems to be going to a dead end. Cold cases annoys the living hell out of me and there is always this feeling of disgust that the perpetrator of a heinous crime might be walking freely on the streets.
These killers thought they were smarter than the law but were finally convicted with the most unlikely of evidences.
http://hubpages.com/politics/Killers-Caught-With-The-Weirdest-Evidences