Witness testimony is an essential part of any criminal trial. That’s why anyone who is called to testify promises to tell the truth and is subject to criminal penalties if they deliberately violate that oath. However, not everyone takes their promises seriously and not every dishonest person is caught.
Furthermore, even people who believe they are honest might still be making mistakes—yet have a strong enough personal presence on the stand that a jury believes them.
This is where a good lawyer comes in. An effective trial lawyer must know how to discredit a witness. This ensures that the case is decided on its factual merits rather than by testimony that is either deceitful or incorrect.
Unfortunately, a lawyer can’t spring from behind the table and say “You’re lying!” and expect to be taken seriously. Discrediting a witness requires diligent preparation behind the scenes and some real finesse at trial.
Regardless of what you might have seen on television, no lawyer is going to be completely blindsided by what a witness says—particularly a defense attorney, who has the right to know what evidence the prosecution is bringing forward.
Witnesses have given pre-trial statements and have likely gone through depositions (an oral questioning). They have put a considerable amount of information on the record. The lawyer has to know this record inside and out. If something different is said on the witness stand, the attorney must point out to the jury that there is an inconsistency in statements.
How to go about this depends on the witness. Let’s say a lawyer is representing someone who was accused of robbing a store. A key witness for the prosecution is an elderly person who was a block away. Perhaps this person has eyesight issues. The defense lawyer doesn’t need to be overly aggressive, but they must certainly ensure the jury knows that it’s very possible the witness honestly misidentified the person.
Now let’s consider another witness. This is someone who may or may not have had a clear view of the crime. On being questioned by police officers on the scene, they repeatedly gave non-committal answers about what they may or may not have seen. But now at trial, they are giving very certain and specific answers that implicate the defendant.
The defense attorney has an obligation to make sure the jury knows that these hard-and-fast answers, filled with certitude, are quite different from the answers that were previously given. It’s quite reasonable to question why they’re surer of themselves now (potentially a year or 2 after the fact) then they were in the moment. Their courtroom testimony might not be dishonest, but may lack credibility.
Finally, we consider a third witness to this crime. The person claims to have identified the defendant as the burglar. This is also a person with a criminal record themselves. Is it permissible for the defense to bring that person’s past into question, as a way of discrediting their testimony?
That depends. Character evidence can be brought in only if it’s relevant to the case. In this example, that would require that it go to the issue of credibility. To pick a slam-dunk answer, if the person was previously convicted of perjury, it’s a safe bet the judge will allow the jury to know that.
But what if the character evidence is not as clear-cut? Let’s say this same witness got a DUI 3 years ago. On the surface, that wouldn’t appear relevant. But what if they were required to go to mandatory alcohol rehab and there’s reason to believe they haven’t been sober?
Let’s further assume this burglary in question took place at a liquor store. What if there’s legitimate reason to wonder if the witness was sober? That would be relevant to their credibility in providing an identification.
Another way of discrediting a witness is simply to counter them with another witness. To stick with our burglary example, maybe there are 2 other people who are equally certain that the defendant is not the person they saw leaving the store. In this case, it’s not necessary to directly undermine the opposing witnesses; simply to ensure the jury knows there are differing opinions out there.
Finally, we come to the strategy of using circumstances to discredit a witness. Consider the classic 1992 military courtroom drama, A Few Good Men. A key piece of secondary evidence was the issue of whether the murder victim was going to be granted a transfer off his base. Proving that no transfer was going to happen would help the defendant’s case.
The military commander insisted on the witness stand that the transfer had been authorized. But the defense used circumstances to discredit the testimony. It was noted that the victim hadn’t packed his clothes and hadn’t made any phone calls, both of which would have been typical behavior for someone about to be transferred off the base early in the morning. The circumstances served to discredit the commander’s testimony.
A lawyer has to have a finely honed eye for detail to effectively discredit testimony. The only way to notice inconsistencies and anomalies is to have a thorough grasp of all the details of the case.