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Arjuna Nagendran

Doctor,

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Is circumstantial evidence enough for conviction?

The talk tagged marks an interesting point - we are increasingly realising the fallibility in being able to trust our own memories - this is particularly disturbing in terms of the reliability we place on witness accounts.

The question is.. if we have to accept that the human memory does employ reconstructive memory, even just some of the time, is circumstantial evidence really enough to convict someone?

Or does this demand that, in pursuit of innocent until proven guilty, we must
move to a system where more than circumstantial evidence is required to succesfully prove guilt?

Interested for peoples' thoughts on this one!

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  • Sep 24 2012: Circumstantial evidence is typically more reliable than direct evidence. Unfortunately, most people don't understand what circumstantial evidence is. Circumstantial evidence is evidence from which another fact can be inferred. For instance, DNA evidence is circumstantial evidence. If a person's DNA is found at the crime scene (more precisely, if DNA matching a person's DNA profile is found at the crime scene) then we can infer that the person (or someone with his identical DNA) was present at some point. Fingerprints are the same -- they tell us that someone touched something. We can then infer that the person with those prints must have been present, or must have held the weapon, or some other fact in controversy. Most scientific evidence is circumstantial. In Mr. Fraser's example, information about the lighting at the scene would be circumstantial evidence, from which we can infer whether the eyewitnesses are likely to be reliable or unreliable.

    Direct evidence is evidence that directly proves a fact without the need to draw an inference of another fact. For example, eyewitness testimony is direct evidence. It is a person saying "that's the man who robbed me." No inference is required, you either trust it or you don't. Likewise, a confession is direct evidence. The evidence that convicted Mr. Carrillo in the case under discussion was direct evidence -- eyewitnesses. Had there been gunshot residue on Mr. Carrillo's hands shortly after the crime, or the correct make and caliber ammunition hidden under his mattress, that would have been circumstantial evidence.

    I realize the original question assumes that the term "circumstantial evidence" means some sort of weaker or less reliable evidence. But to be precise, I think the correct terminology is important.

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