Serious crimes happen every day, and solving them is a complicated process. Unlike in movies and on television shows, murders and other serious criminal acts take time and the right expertise to solve.
The success of police and detectives in solving these crimes is a part of a group effort. Behind the scenes, it is the job of unbiased forensic scientists to examine and analyze items of evidence that will ultimately uncover the truth in criminal cases. By understanding the basics of criminal investigation and the use of forensic science, people can better understand what it takes to solve a crime.
The Crime Scene
The crime scene is arguably the most important place to collect evidence when investigating a crime. Its size and scope are typically dependent on the type and magnitude of the crime. This area is closed off to the public to prevent evidence from being removed or tampered with. When detectives arrive at a crime scene, they are presented with a situation that they must determine the cause of. To do that, they must be able to establish what the sequence of events was leading up to the crime and after it.
Crime scene investigators will fastidiously collect any articles of evidence present. Evidence comes in many forms, and no detail is considered insignificant in the collection process. It may include clothing or weaponry such as guns, bullets, or knives. Impressions, including tire tracks, footprints, and fingerprints, are also types of evidence, as are hair, fibers, and fluids such as blood, semen, or saliva. Depending on the crime, other items of evidence may include notes, documents, or broken glass. Found items are kept in plastic evidence bags or jars, properly labeled, and entered into an evidence log.
Labels should include the collector’s initials and their identification number, a description, an evidence number, and the location, date, and time. During this process, criminal investigators must wear gloves and a protective suit to avoid contaminating anything that they come across. The collection process also involves preserving the scene with detailed photographs, videos, and drawings. This should be done immediately, particularly in high-traffic or public areas. Measurements are also necessary, as are detailed notes. This evidence is then sent to laboratories and forensic scientists for testing and evaluation.
Examining the Body for Evidence
In certain situations, the crime under investigation was not committed at the scene where it was discovered. If an individual was murdered at one location but their body was dumped at another, for example, the crime scene will only provide limited clues as to what actually happened. In these situations, the body of the victim will often be the best source of evidence.
Prior to moving the body, it must be photographed without anything being altered or removed. Pictures must be taken from all angles and in a way that any wounds or injuries are recorded. Only after the evidence collection process is completed is the body removed and sent to the mortuary.
At the mortuary, an autopsy is performed by a forensic pathologist. The autopsy is a way to investigate the specific cause of death and will look for evidence of physical or chemical injury or poisoning. The evaluation of the body will help determine whether the cause of death coincides with any evidence or statements taken at the crime scene. This examination involves an external evaluation of the body and an internal one in which bones and other inner structures and organs are studied. When a body has suffered from severe decomposition, the only way to identify it may be with dental records or DNA.
The Role of Witnesses and Suspects
In addition to material evidence, police and detectives also gather oral evidence from people who may have seen or heard anything related to the crime in question. The people they speak with may be either witnesses or suspects. Investigators often take statements from a number of witnesses and compare responses, as there are often disparities in how events are remembered. People who are suspects are interviewed differently than witnesses. Often, their interviews are performed at the police station, and they may be held in custody. Their interviews are often longer and more intense, with detectives asking repeated questions and using psychological tactics to uncover inconsistencies in their statements. When a suspect is interviewed, blood and a DNA sample are often taken.
At the Forensic Lab
At the police laboratory, forensic scientists use a range of techniques and equipment to test evidence or samples taken from the crime scene, victims, and suspects, including microscopes and state-of-the-art equipment. To test for chemicals, for example, scientists use gas chromatography and mass spectrometry. The samples collected and the specifics of the crime help to determine which tests or examinations are appropriate. Testing can help scientists link a suspect to a crime. Once the testing is done, the results must be interpreted and documented. Scientists must be confident in their results and are often called to testify in court as expert witnesses.
The Importance of Forensic Science
Forensic science is critical to crime scene investigation. Its use helps authorities secure justice for victims while helping to ensure that the guilty party is prosecuted for the crime and innocent suspects are cleared of any wrongdoing. The use of forensic science can provide proof of a suspect’s presence at a crime scene, and it can contradict or confirm testimony. By-the-book handling of evidence and careful and methodical forensic testing are requirements that can impact the effectiveness of the forensic professional and the evidence in a court of law.
- What Is a Forensic Pathologist?
- Let’s Keep the Science in Forensic Science
- Forensic Science: Fact and Fiction
- What Is Forensic Science?
- Forensic Science in the Crime Lab (video)
- The Real CSI
- Becoming a Forensic Science Technician
- Types of Forensic Tests
- Forensic Evidence Types
- Serology: Blood and Other Bodily Fluids
- What Do Forensic Scientists Do?
- How it’s Done
- How Crime Scene Investigation Works
- Understanding the Impact of the Forensic Sciences on the Criminal Justice System
- How Science Is Putting a New Face on Crime-Solving
- Forensic Science Communication: Hair Evidence
- Five Types of Pattern Evidence All Investigators Should Know
- Leaving a Trace: Forensic Science Through History
- Bodily Fluids Analysis
- DNA Testing Methods
- Biological Evidence: Forensic Biology
- Trace Evidence: How Fibers and Hair Are Used to Aid in Crime-Solving (PDF)
- Glass Fragments for Forensic Analysis (PDF)
- How to Collect Evidence at a Crime Scene
- Proper Collection, Documentation, and Storage of Wood Evidence From a Crime Scene(PDF)
- Preserving and Collecting Forensic Evidence (PDF)
- From the Crime Scene to the Courtroom: The Journey of a DNA Sample
- Recent Advances in Forensic Ballistics
- Physical Match Examinations
- Forensic Science History