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How Expert Witnesses are used in Criminal Defense Cases

Expert Witness in Louisville, KY

In many criminal cases, expert witnesses are used by the prosecution to testify on certain facts and evidence. The defense also has the right to call expert witnesses to testify on their behalf and to rebut the prosecution’s testimony.

What is an Expert Witness?

When it comes to expert witnesses, the term “witness” is kind of a misnomer. Most often, those who are brought in to provide expert testimony did not actually witness the crime, although sometimes, an expert witness could be the arresting officer. Either way, expert witnesses are not there primarily to testify about what they witnessed personally that may make it more or less likely that the defendant committed the crime they are charged with. Rather, they are there to lend their expertise to help give the court additional insight into various facts and pieces of evidence in the case.

Types of Expert Witnesses in a Criminal Trial

An expert witness is supposed to be distinguished in his or her area of specialty because of their experience, skills, knowledge, and training on the subject matter for which they are opining and/or testifying. Their value is in their ability to speak credibly and authoritatively regarding a particular factor (or set of factors).

There are numerous types of expert witnesses that may be called by the prosecution or defense in a criminal trial, some of the most common include:

  • Criminology experts
  • Forensic chemists
  • Forensic toxicologists
  • Forensic pharmacologists
  • Fingerprint examiners
  • DNA testing experts
  • Breath test experts
  • Drug recognition experts
  • Gang psychology experts
  • Firearms and ballistics experts

How are Expert Witnesses Used in a Criminal Trial?

There are two general types of expert witnesses:

  • Consulting Experts: Consulting experts work behind the scenes to assist the legal team with various aspects of the case. For example, a consulting expert may review certain pieces of information that fall within their area of expertise, provide advice and counsel, and assist the team with legal strategy. If an expert is retained purely for consulting purposes, the other side may never know that they were consulted in the case.
  • Testifying Experts: A testifying expert is one who the prosecution or defense is prepared to call to the witness stand at trial (if necessary). This type of expert witness should have strong communication skills and the ability to make complex subject matter understandable to the average layperson. They should also have previous testifying experience, so they are comfortable inside the courtroom and they are able to withstand vigorous cross-examination. Testifying experts need to be chosen carefully, because their presence on the case must be disclosed to the other side.

For experts who are planning to testify in a criminal proceeding, a written report may also be required to accompany their testimony. The report may contain information about the witness’s credentials, their findings and opinions, and what they believe should happen with the case (based on their findings and opinions).

How an Expert Witness may be Used in a Drug Case

In many drug possession cases, the prosecution may call a police expert witness to try to convince the court that the defendant intended to distribute the drugs. Although a salaried police officer is almost never an objective, unbiased witness, courts will often allow them to testify as to whether the drugs were intended for sale. The officer may present some standard reasons why they believe the defendant intended to sell the drugs; such as the defendant possessing a large amount of cash, the drugs being divided into small packets, and other circumstantial evidence.

The defense can challenge this testimony in a number of ways. For example, the defense could bring in their own expert on drug packaging and distribution to review the case and testify that the drugs and paraphernalia (that were obtained during the arrest) are consistent with personal use. If, based on the circumstances of the case, the defense’s expert can rebut the officer’s testimony and credibly claim that the drugs possessed by the defendant were for personal use only, this could result in a reduction to a lesser charge, which would carry fewer penalties and in many cases, keep the defendant out of jail. Another potential defense strategy may be to identify various weaknesses in the officer’s testimony and expose these weaknesses to the court through aggressive cross-examination.

Charged with a Crime in Kentucky? Contact an Experienced Criminal Defense Attorney

If you are facing criminal charges, a conviction could carry harsh consequences; which may include heavy fines, jail time, and many others. With so much on the line, you need a skilled criminal defense attorney in your corner who is able to employ a wide range of defense strategies, including the use of expert witnesses and/or the ability to effectively challenge the testimony of expert witnesses presented by the Commonwealth.

Attorney Ron Aslam has in-depth experience successfully defending individuals facing all types of criminal charges in Kentucky. Ron is a former prosecutor who has worked for many years on both sides in a criminal proceeding. Ron understands the mindset of prosecutors, and he knows the common tactics they use to try to obtain a conviction. He can thoroughly review your case and explore all potential legal avenues that will help mitigate the situation as much as possible.

Call our office today at 502-581-1676 to schedule an initial consultation with Attorney Ron Aslam. You may send us a message through our online contact form or stop by our Louisville office in person at your convenience.