My wife and I often watch "Forensic Files" on Court TV which covers various homicides. What this program demonstrates is that it does take some due diligence to properly investigate a potential homicide, but dedicated people who care can do proper investigation and follow up.
A few years ago during the Starbucks investigation, the suspect came downtown for questioning and one of the detectives noticed a dried, red substance on the suspect's shoe. Did the detective demand that the suspect take off his shoe so that the substance could be tested? No, he let him walk out after the questioning was through. Weeks later the police got a warrant and searched the suspect's home but could no longer find that particular pair of shoes in his closet. Duh!