I am familiar with lawyers' notion of evidence: direct evidence and circumstantial evidence. To scientists, what is evidence, and must it always be direct or may it be circumstantial?

A scientists' evidence which is 'forensic/dna' is based on their scientific knowledge to the case. Since they are not trying to win a case like lawyers are (whether right or wrong) they try to emphasize that the DNA evidence is as strong and reliable as it can be, truthfully. They know it should always be considered with other physical and circumstantial evidence of motive, means and opportunity. Even tho it's mostly always direct, forensic evidence 'can' also be circumstantial.

One example is that a disputed form of DNA testing done on a hair found on Scott Peterson's boat was 'circumstantial evidence' because the DNA was called 'mitochondrial' and the chances were that the mitochondrial DNA from the hair could be found in one out of every 112 whites.

Evidence.

Thanks folks. A lot seems to depend on the probability of anything which has to pass for evidence, whether scientific or legal, being factual.