There is a rule that Ka'asher Zamam vilo Ka'asher Asa: the second set of witnesses have to appear in court "before the punishment" in order that the first witnesses get the punishment Ka'asher Zamam. ...
There is a concept of Edim Zomemim (Wikipedia has it translated as "Collusive Witnesses") (עדים זוממים). Basically, if two witnesses testify about someone, and then two other witnesses come and say ...
If a person kills and there are only two witnesses and one witness has killed by accident before, are there two witnesses, or does the one who killed before not count?