1. It first must be shown that the defendant made an agreement with a person to testify falsely - might be the toughest bar, certainly if it's only Cohen's word vs. Trump. I have a sneaking suspicion there are other witnesses to this though. PENDING.
2. There must be proof that perjury has in fact been committed - Cohen's testimony is on the record and he's admitting he lied. DONE.
3. That the statements of the perjurer were material - See #2. DONE.
4. The prosecutor must also provide evidence that the perjurer made such statements willfully with knowledge of their falsity - See #2. DONE.
5. There must be proof that the procurer had knowledge that the perjurer's statements were false - See #1. PENDING.