I said "no"....but my real answer is "it depends."
It depends on what we mean by "false witness".
Is it someone who is really just "making something up? (for publicity perhaps?) In that case, Yes.
Is it someone who really thought they saw something, but after being questioned, turned out he was mistaken, or turns out he really isn't sure what he saw? Then my answer is No.
You definitely need to discourage being bringing forth bogus accounts. However, you don't want to discourage people who believe they have real data, but might be afraid to come forward because they have "some doubt" about what they might have actually seen.
