Expert witnesses are critical for both the prosecution and defense in a murder trial. The goal of the expert witness is to use their experience about the topic to convince the jury or judge of a particular story that may implicate or eliminate the defendant, depending on whether they are testifying for the prosecution or defense.
Ballistics
Ballistics experts can determine information about the gun used in a murder and help connect a gun or bullets to a particular weapon or person. When a bullet leaves the gun, the gun leaves unique markings on the bullet. This allows a ballistics expert to match the bullet to a specific weapon. Stippling around the entrance wound can show how far away the gun was fired. If a person left fingerprints on the weapon and claimed the weapon accidentally discharge from a far distance, but the stippling evidence shows the injury had to have occurred with the gun less than a few inches away from the victim, this would dispute the defendant's story.
Blood Spatter
Blood spatter has unique characteristics that can tell a story. Drops of blood create distinctive shapes based on how they occur, such as flinging blood that might occur as a victim is repeatedly hit with an object or stabbed, versus if blood is dropped directly on the floor from the victim. One example would be a case where the defendant claimed an intruder broke into their home and stabbed them, then murdered others in the house. If the defendant claimed they were lying down when they were stabbed multiple times, an expert would expect to find some of their blood spattered around the scene since the stabbing motion causes blood to spatter on the walls. If the only place the defendant's blood is found is in droplets on the floor, it would imply they were standing when the stabbing occurred. This could be used against the defendant if the prosecution suspects they were the actual murderer and fabricated the story of being a victim of the intruder.
Medical Examiner
The expert testimony of the medical examiner is one of the most crucial aspects of a murder case. The goal of the defense depends on their strategy. In cases where the defendant is trying to prove they did not do the murder, certain details can make the case of innocence. For example, an approximate time of death combined with a solid alibi is used to show the defendant could not have committed the crime. If the goal is to prove the murder was a case of self-defense, the manner in which the victim died can be used to prove their case. A defendant claiming self-defense would have a hard time convincing a judge or jury if the medical examiner determined the entrance wounds from either a knife or gun were in the back of the victim.
There are several types of expert witnesses services that use their experience, education, and science to reach conclusions about the murder and help the judge or jury visualize what happened to the victim. In some cases, the verdict often hinges on how convincing the expert testimony is on one side or the other.
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