system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The Troy Davis Case

I was reading wikipedia and I just didn't get their explanation.

What was the background? What were some evidence for and against him?
gpt
Cop was shot. Davis was charged and convicted. Some of the forensic evidence (from a pair of shorts that had been taken from his house without a warrant) was not allowed in court, and the physical evidence was quite weak (no murder weapon, but the bullet casings found at the scene matched the casings of another shooting he was charged - but not convicted - with) so the prosecution relied entirely on eyewitness testimony. There were 9 non-police witnesses (I don't know where people are getting numbers like 7 or 34; there were 9). He was found guilty.

That was about twenty years ago. More recently, 7 of the 9 have changed or entirely went back on their testimony. Some of them are now saying it was another guy (who, by the way, is one of the 2 who did not change his testimony), and some are saying that the cops coerced them into accusing Davis. 

The controversy is that, while the conviction DID happen, it was about as shaky as a conviction with a death penalty can be. Since then, much of the evidence that they relied upon has either turned out to be wrong, or to at the very least to raise substantial questions about it. The fact that he was executed when the legal system cannot have been 100% is a problem.