Impeachment of a witness is conducted by the

Impeachment of a witness is conducted by the opposing party on cross-examination of the witness.

Explanation:

This process is carried out in civil and criminal cases and has two types of questions:

On the one hand, those that give a presentation of the facts and detail everything that was not taken into account in the direct examination.

And on the other hand, those that question the credibility of the witness.

The attorney in charge of the process has the power to use the repetition to investigate the testimony and ask questions demanding an answer, without harassing the witness.

In simple words: with impeachment what is sought is to demonstrate that the witness may be giving an erroneous testimony (either intentionally or not) by reviewing the evidence.