I was reading Hammurabi's code the other day and was struck by the fact that the very first thing the code does is establish the consequences for bearing false witness. There's not even an allowance for "well, I thought it was true", if you are accusing another in court then you are running the risk of the same penalty that you are hoping to impose on the other person, whatever penalty that may be.

There are lots of problems with Hammurabi's code and I wouldn't suggest emulating this particular implementation, but it's interesting to note just how far back this concern of false accusations goes and how our legal system seems to have backslid a bit in this regard.

http://www.wright.edu/~christopher.oldstone-moore/Hamm.htm