What Is a Detective's Role in a Trial?
In any given criminal trial, three different sets of investigators may be involved at the same time. Defense investigators work to flesh out evidence for defense attorneys. Police detectives, along with a district attorney's investigators, work to support the prosecution of a case. All of these investigators may be asked to testify at trial.
The first detectives to be involved in a criminal case are usually police detectives. Police detectives may be general investigators in charge of investigating many different types of crimes, homicide detectives in charge of murder investigations, drug investigators or financial crimes investigators. All types of police detectives interview witnesses to determine whether a crime was committed and who was responsible. Once they determine that a suspect can be charged with the crime, police detectives gather enough evidence to support a successful prosecution. Once the trial begins, the police detective presents the evidence to the jury under cross-examination from both the prosecutor and the defense attorney. He answers any questions about how the evidence was gathered and what the evidence is and tries to act as an advocate for the victims of the crime.
District Attorney's Investigators
Once criminal charges are brought to the district attorney, the district attorney's office may bring its own detectives onto the case. District attorney's investigators are not private detectives but law enforcement officers who work for the district attorney directly rather than the police department. They perform many of the same investigative duties as police detectives, and they can also be called upon to testify at trial. Just like police detectives, they are subjected to cross-examination by the defense.
Defense investigators check every detail of the evidence presented by the prosecution. For instance, if police detectives claim they found certain items in the suspect's house, defense detectives would likely check the photographs from the crime scene to see if they match what the police detectives describe. Defense detectives also interview prosecution witnesses to find out if their stories are consistent, and they seek out other witnesses who may have alternative accounts of what happened. Any inconsistency with the evidence presented by the prosecution becomes a key piece of evidence for the defense. When defense detectives testify at trial, they present their evidence and answer questions about it under cross-examination.
Because of the adversarial nature of a criminal trial, none of the parties involved can be counted on to be perfectly objective. Police detectives see themselves as victim's advocates but may sometimes interpret evidence to build a case against a particular suspect even though the evidence could be interpreted another way. Prosecuting attorneys are responsible for convicting the accused, and defense attorneys are responsible for making sure he gets justice. Detectives who work for the defense, the prosecution or the police department must collect evidence and present it as convincingly as possible in court while defending their evidence against aggressive questioning. The attorneys for the other side will always try to find weaknesses or flaws in the detective's testimony.
Scott Thompson has been writing professionally since 1990, beginning with the "Pequawket Valley News." He is the author of nine published books on topics such as history, martial arts, poetry and fantasy fiction. His work has also appeared in "Talebones" magazine and the "Strange Pleasures" anthology.