Can a person testify if he or she has committed a felony and lies under oath by saying that he or she has not?

A felony conviction does not prevent a person from testifying as a witness. Depending on how long ago the conviction occurred, the witness could be confronted with it in front of the jury. This is called "impeachment." In many states, the judge can instruct the jury that they may consider the witness's prior felony conviction in deciding how much credibility to give the witness's testimony. If the witness lies and denies the existence of a prior felony conviction, he or she could be charged with perjury.