Is It Possible to Discredit a Private Investigator in a Divorce Case?

by Stephanie Reid
Private investigators can be discredited by showing a lack of personal knowledge of the case.

Private investigators can be discredited by showing a lack of personal knowledge of the case.

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If you are concerned about the testimony of a private investigator in your upcoming divorce case, there are several ways you may be able to discredit that person through cross-examination. The rules of evidence are found in every state’s code and provide a set of guidelines for the admissibility of testimony and documents. Certain evidence about a private investigator may be admissible to prove a prior criminal record, history of perjury or other misconduct. However, not all negative aspects of a witness’s background are admissible, such as certain types of character evidence.

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Criminal Record

If the private investigator has been convicted of perjury in the past, this information is absolutely relevant and should be revealed on cross-examination. Many states maintain a rule that if either party is aware a witness has perjured himself in the past, he must make the court aware. You may also be able to cross-examine the investigator about any history of felony or misdemeanor convictions if the conviction occurred within a certain number of years. Questioning the investigator about arrests or convictions for crimes other than perjury more than 10 years old likely won't be allowed by the judge.

Prior Inconsistent Statement

If the private investigator has offered inconsistent testimony, you may be able to impeach him by entering evidence of his prior inconsistent statement. Evidentiary rules are very particular about the type of evidence you can enter to show inconsistency. For instance, if the investigator testified under oath at a previous hearing that he observed a certain situation and is now testifying to a different set of facts, the transcript of the prior hearing may be admissible to show the inconsistency. A transcript from a deposition may also be admissible against the investigator to show inconsistency. This type of evidence will not result in an exclusion of the witness’s testimony, but it will help build doubt in the court’s mind as to the believability of the investigator as a witness.

Authentication of Photographs

A private investigator will undoubtedly accompany his testimony with photographic evidence of alleged misconduct. Fortunately, photographs are covered by rules of evidence and must be authenticated prior to being admitted for consideration. In general, the investigator must provide background facts to satisfy the court that the images in the picture are what the witness claims them to be. If the images are blurry or hard to make out, you can challenge the authenticity of the photos and assert the evidence is unreliable. If the private investigator is unable to offer additional identifying information, his photographs may be excluded.


If the opposing party is seeking to classify the private investigator as an expert witness, you can cross-examine him on his credentials. If a court determines a witness to be an expert, that witness is then empowered to offer opinion testimony not based on solid fact or personal observation. For this reason, the court will require the purported expert to provide evidence of his credentials. In the context of a private investigator, this could include former work as a detective or experience with the Secret Service. It will then be up to the court to decide whether the witness meets the criteria of an expert.