Pro bono means denoting work undertaken without charge, especially legal work for a client with a low income. It is a professional work undertaken voluntarily and without payment. Pro bono cases are dealt to provide services to those who are unable to afford them.
Subpoena means to order someone to go to a court of law to answer questions or to order the appearance of documents in a court of law.E.g:
A friend of the victim was subpoenaed as a witness by lawyers representing the accused. They were subpoenaed to testify before the judge.
A deposition is the taking of an oral statement of a witness under oath, before trial. It has two purposes: To find out what the witness knows, and to preserve that witness’ testimony. The intent is to allow the parties to learn all of the facts before the trial, so that no one is surprised at trial.
A perjury is the offense of willfully telling an untruth in a court after having taken an oath or affirmation.
He claimed two witnesses at his trial had committed perjury.