What is the 'chain of custody' of CSI?

What is the 'chain of custody' of CSI?

Richard Saferstein (Former Chief Forensic Scientist) gives expert video advice on: What is a 'mobile crime laboratory'?; What physical evidence is important for an investigator to collect at a crime scene?; What evidence should a forensic scientist collect from the body of a murder victim? and more...

When you go to court as a forensic scientist, one of the things that you're almost always confronted with is the issue of chain of custody. Many of the participants in the court case don't have much of a background in science, but they do have thorough knowledge about this concept of chain of custody. How do you know the evidence that you're testifying about? How do you know that the evidence that was examined in the crime lab was the item that actually was collected at the crime scene? It has to be documented. The flow of the evidence from the scene to the lab, to the courtroom, must be documented. Essentially, chain of custody means accountability and being able to know where that evidence was at all times, from the moment it was found to the moment it's being testified to. Also, at the same time knowing that it wasn't contaminated, and knowing that its integrity was not impugned in any way.