Crime Scene Technicians (CSTs) are forensic specialists tasked with the systematic recognition, documentation, and recovery of physical evidence that may link a perpetrator to a victim or location. CSTs apply scientific principles and specialized tools to preserve the details of an event. Their methodical approach ensures that physical evidence is collected in a manner that maintains its integrity and admissibility for later analysis and presentation in court.
What is a Crime Scene Technician?
A Crime Scene Technician is a highly specialized, non-investigative role focused on the technical processing of a physical location. Unlike detectives or patrol officers, a CST’s primary function is to apply forensic science to the scene itself, rather than interview witnesses or pursue leads. The role is known by various official titles, including Crime Scene Investigator (CSI), Forensic Technician, or Evidence Technician, depending on the employing agency. CSTs provide a technical service that supports the larger investigation by documenting the scene’s condition and collecting all relevant physical material.
Securing and Documenting the Scene
The first responsibility of a CST upon arrival is to establish and maintain a secure perimeter, often referred to as establishing the chain of custody boundary. This process involves creating multiple zones of security with a single, controlled access point to prevent unauthorized entry and potential contamination. All personnel entering and exiting the core crime scene must log their names, times, and purpose of entry to maintain a comprehensive record of scene integrity. The technician begins a meticulous documentation phase before any physical evidence is touched or moved.
Comprehensive documentation starts with photography, capturing the scene through three distinct perspectives. Overall photographs provide a broad view of the entire scene and its relationship to the surrounding environment. Mid-range photographs focus on the spatial relationship between individual items of evidence and fixed objects, establishing context. Close-up photographs capture the minute details of each piece of evidence. These close-ups are always taken twice: once to show context and once with a measurement scale included for accurate sizing.
Following photography, the technician creates detailed sketches and maps to record precise measurements and object placement. A rough sketch is drawn at the scene, which is later converted into a finished, scaled diagram using computer-aided drafting software. Mapping evidence locations commonly employs techniques like triangulation or the rectangular coordinate method. This process ensures a permanent, measurable record of the scene’s condition.
Methods of Evidence Collection and Processing
The physical recovery of evidence requires specialized techniques tailored to the material being collected, all aimed at preventing cross-contamination and degradation. Latent prints, which are invisible impressions left by skin oils and perspiration, are developed using physical or chemical methods. Techniques include applying fine magnetic or fluorescent powders to non-porous surfaces or using fuming processes, such as cyanoacrylate (superglue) fuming, to stabilize the print on the object. Once visualized, the latent print is permanently recorded through specialized photography or lifting with adhesive materials.
Biological evidence, such as blood, saliva, or semen, is collected using sterile cotton swabs that are then air-dried to prevent DNA degradation. Bloodstain pattern analysis involves studying the size, shape, and distribution of bloodstains to determine the actions that created them. Trace evidence, including hairs, fibers, paint chips, or glass fragments, is often collected using specialized tape lifts or high-efficiency vacuum devices. Each sample is then meticulously packaged in a paper container or a “druggist’s fold” to prevent loss of the microscopic material.
Ballistics and tool mark evidence require careful preservation of characteristic marks left on an object. A spent bullet or cartridge casing is handled minimally, often with gloved hands or forceps, to avoid scratching or contaminating the surface with transfer DNA. Tool marks, which are unique striations left by a tool on a softer surface, are first documented photographically with a scale before the entire object is collected or a cast of the impression is made. Proper packaging for these items involves securing them in solid containers so that the delicate impression or microscopic marks are not damaged during transit to the laboratory.
Responsibilities Beyond the Crime Scene
The CST’s work continues long after departing the physical location, focusing on the administrative and legal requirements that ensure admissibility in court. Every item collected must be meticulously packaged in a separate container, sealed with tamper-evident tape bearing the technician’s initials and the date. This packaging is labeled with unique identifiers, including the case number, item number, and a brief description of the contents. Strict maintenance of the chain of custody is required for all evidence collected.
The chain of custody is a chronological, written record detailing the control, transfer, and disposition of evidence from the moment of collection onward. This documentation proves that the evidence presented in court is the same item recovered at the scene and that it has not been altered or contaminated. Each time the evidence changes hands, the transfer must be logged, with the date, time, and signatures of both the relinquishing and receiving parties recorded. Failure to maintain an unbroken chain of custody can lead to the evidence being excluded from legal proceedings, irrespective of its scientific value.
CSTs often assume the role of expert witnesses, testifying in court about the procedures they followed at the scene. The technician must clearly articulate their methodology, documentation protocols, and the meaning of the physical evidence to a lay audience, such as a jury. Testimony is limited to the facts and scientific observations they made, requiring the ability to translate complex forensic science into understandable terms while maintaining objectivity during examination.
Education and Training Requirements
A career as a Crime Scene Technician typically requires a foundation in higher education, with most entry-level positions seeking a bachelor’s degree. Common fields of study include Forensic Science, Chemistry, Biology, or Criminal Justice, with a strong emphasis on laboratory science coursework. Many agencies also require new hires to complete an intensive, specialized training academy or a period of on-the-job training under the supervision of experienced personnel.
Specialized field certifications are pursued by practicing CSTs to develop expertise in niche areas of forensic science. These courses often involve practical exercises to develop the skills needed for scene reconstruction. Continuous professional development through specialized coursework is a standard expectation for maintaining competency in the field.
Essential Skills for Success
Beyond technical knowledge, successful CSTs rely on a set of non-technical attributes to perform their duties effectively. Meticulous attention to detail is required, as the smallest trace material can be crucial to an investigation. The ability to maintain composure and emotional stability is necessary, as technicians routinely work at scenes involving serious trauma. Strong observational skills are required to systematically scan and process a scene, recognizing subtle patterns and inconsistencies. CSTs must also possess clear verbal and written communication skills to produce accurate reports and provide objective testimony in a courtroom setting.