Uh, no. They don’t. Havving had to clean up several crime scenes, including one extremely blood soaked crime scene, they don’t even do clean-up. The crime victim is also responsible to clean up after the criminalists have gone through the scene and left everything the victim owns covered in fingerprint dusting powder. Nor is there an actual duty to really catch the perpetrator, only to take a report.
Fair enough. You’re right. I guess I meant to say “examine the crime scene for evidence” but used sloppy language. My main point was that their job is to catch people after the fact, they have no duty to prevent a crime.