Criminal investigation is defined as ”a reconstruction of a past event,” through which police personnel solve crimes (Osterberg and Ward 2004, 5). Detectives or other investigative personnel take numerous factors into consideration when reconstructing a case in order to determine who committed the crime and under what circumstances the crime was committed. Personnel who perform criminal investigations must have certain characteristics and abilities in order to do the job successfully. Great care is taken in selecting those who perform criminal investigations.

Very broadly, the objectives of the criminal investigation process are (1) to establish that a crime was actually committed,

(2) to identify and apprehend the suspect(s),

(3) to recover stolen property, and (4) to assist in the prosecution of the person(s) charged with the crime (Swanson et al. 2006, 50).

The three major functions performed at the crime scene as part of the investigative process are overall coordination of the scene, technical services, and investigative services (Swanson et al. 2006). Most crime scenes require someone who coordinates the crime scene, due to the numerous responsibilities involved in the process. This person is ultimately responsible for everything that goes on at the crime scene. Technical services are performed by crime laboratory personnel, civilian evidence technicians, or sworn law enforcement personnel who are responsible for collecting and processing evidence. Investigative services include gathering information from people, including victims, witnesses, or other people who were in the vicinity of the criminal activity, but may not have necessarily known that.

Various factors affect the criminal investigation process. The more significant factors include the size of the organization, type of the organization, geographical location of the organization, and the philosophy of the organization. Most agencies are affected by more than one of these factors simultaneously, in varying degrees. The size of the organization may affect the resources of the organization, thereby dictating how many personnel might be allocated to perform criminal investigation duties. In larger organizations, there tends to be more specialization of duties, which means that there is a great likelihood that criminal investigation might consist of an entire unit. In contrast, in smaller organizations, which constitute roughly 90% of local police organizations, the likelihood that criminal investigation will comprise an entire unit is minimal. In small organizations, it is not unusual for all personnel to perform criminal investigations. In the larger, more specialized organizations, it is unusual for several personnel to be involved in the criminal investigation process.

The type of organization affects the criminal investigation process as a result of its mission. For example, local organizations are more likely to perform all general criminal investigations, whereas federal organizations have a narrower focus, such as the Drug Enforcement Administration, which focuses primarily on drug investigation and interdiction.

The geographical location of the organization can also affect the type of criminal investigations that the agency performs. Agencies that have coastal borders would be more than likely to have a greater number of crimes that involve the coastline or water. In other states, in the Midwest for example, crimes involving farming and agriculture would be more prevalent.

The philosophy of the organization may also affect the criminal investigation process, both in formal and informal ways. Policies will dictate some of the investigation process and could be additionally affected by the internal and external politics of the community. Informally, if the administration lets its desires be known with respect to types of investigations to pursue, this could also have an effect on the criminal investigation process.

Phases of Criminal Investigation

The criminal investigation process consists of two primary phases: the preliminary investigation and the follow-up investigation.

Preliminary Investigation

The steps of the preliminary investigation are (1) receipt of information, initial response, and officer safety procedures; (2) emergency care; (3) secure and control persons at the scene; (4) issue a be-on-the-lookout; (5) evidence procedures generally; and (6) the incident/offense report (Swanson et al. 2006, 53-58).

Information typically originates with the victim or a witness to a police dispatcher and then to whomever is responding to the call, which is usually a uniformed patrol officer. Regardless of the size of the organization, a uniformed patrol officer usually makes the initial response. At the scene, if an organization has a criminal investigation unit, it is determined whether or not to turn the case over to a detective. The initial response will vary based on the type of case, and officer safety is paramount regardless of the type of call. Emergency care for anyone at the scene, including the suspect, is a primary consideration. Prior to taking further action, the responding officer must identify and control the crime scene, followed by issuing a “be-on-the-lookout” order as needed. In most organizations, even the smaller ones, an officer will be joined by additional personnel to help identify and gather evidence. Finally, an offense report must be completed documenting the circumstances of the criminal activity, which is basically the reconstruction of events, as stated previously. The offense report serves as the foundational basis for further follow-up of the investigation.

Follow-Up Investigation

Procedures vary from organization to organization regarding whether or not to continue the preliminary investigation with a follow-up investigation, which is the secondary information gathering phase following the preliminary investigation and prior to the closing of the case (Swanson et al. 2006). Typically the larger the organization, the more elaborate the process is for determining whether or not to proceed with a follow-up. Some organizations use solvability factors to determine whether or not to pursue a case. Solvability factors use a system of weighting in which values are assigned to certain case characteristics. The total of the weights have to meet a certain numerical value, or threshold, in order for the case to be pursued. Examples of case characteristics that are considered include, but are not limited to, the naming of a suspect, the presence of physical evidence, whether or not there are any witnesses, and whether or not the crime fits an established modus operandi (MO) (Swanson et al. 2006).

As with the preliminary investigation, certain steps must be adhered to during the follow-up investigation: (1) further examination of physical evidence, (2) neighborhood and vehicle canvasses, (3) checking pertinent databases, and (4) interviewing victims and witnesses (Swanson et al. 2006).

Further examination is typically performed at a crime lab unless the organization is large enough to have its own lab. Neighborhood and vehicle canvasses provide detectives the opportunity to gather information from people in proximity to where the event occurred. Oftentimes, citizens provide useful information to police without even knowing that the information is related to a crime. Numerous databases are available to police personnel for the follow-up investigation. The National Crime Information Center (NCIC), which is maintained by the Federal Bureau of Investigation, is one of the most comprehensive sources of information. The NCIC database includes information such as a stolen vehicle file, a stolen gun file, a wanted persons file, and a terrorist file.


Oftentimes, research will be conducted to evaluate the effectiveness of certain procedures or practices in order to improve the work that is being evaluated. The most significant work examining the process of criminal investigation was the RAND study by Greenwood, Chaiken, and Peter-silia (1975). This study found that 80% of serious crime cases were never solved, and of those that were solved, most of the cases were solved because of information gathered from witnesses and patrol officers rather than because of detectives or forensic science. Greenwood and colleagues also found that physical evidence was often collected at crime scenes, but most of it was never analyzed and it was rare for physical evidence to lead the police to a suspect.

Following the RAND study, Eck (1983) and the Police Executive Research Forum (PERF) came to similar conclusions. Eck examined robberies and burglaries in three jurisdictions. He found that follow-up work performed by detectives contributed to solving some cases. Use of physical evidence, though, while readily available, was still limited. The detective activities that contributed the most to crime solving were searching for additional witnesses, contacting informants, talking to other officers, and using police records—not using physical evidence or forensic science. Consequently, it appears that gathering information from people appears to be more valuable than using physical evidence recovered at a crime scene.

Processing the Crime Scene

Processing the crime scene should follow routine protocol under most circumstances. Following a systematic process provides for the likelihood of the most thorough collection of evidence at the scene. Comprehensive crime scene processing consists of the following components: (1) developing a plan of action, (2) note taking, (3) crime scene search, (4) crime scene photography, (5) sketching the crime scene, and (6) collection of evidence (Fisher 2004).

The plan of action will vary from crime to crime, but it is important to do an initial assessment of the scene to ensure that all aspects of the crime are covered. Note taking should be done throughout the entire process. These notes may be used in court by both the prosecution and the defense. The crime scene search should cover the entire area within the crime scene boundaries, but also should take into consideration the areas surrounding the crime scene. Although it is ideal to control the entire crime scene, evidence might leave the crime scene as personnel go in and out of it. So, it is wise to search whatever is within reasonable proximity to the crime scene.

Photographing the crime scene with multiple views of relevant items is necessary. Photographs provide visuals of objects in their original states and also aid in demonstrating size, with the use of measuring tools that are also present in the photographs. Sketching the crime scene as it appears upon the first respon-der’s arrival is imperative because objects or even people may be moved during the course of processing the scene. Typically a rough sketch is done at the crime scene and a final sketch, usually for use in court, is done after the scene is processed and sometimes with technological aids for computer-aided drawing.

Finally, collecting and packaging evidence must be done. This is tedious work that requires strict adherence to policies and procedures in order to not damage the evidence. Criminalistics, the science dealing with the interpretation of physical evidence, is used frequently when trying to solve crimes. Some form of physical evidence is always present at a crime scene whether it is visible to the naked eye or not. The examination of the crime scene for physical evidence often constitutes a major part of the tasks that must be performed by various personnel.

Physical Evidence

One of the most important considerations regarding physical evidence is that every crime scene has to be treated individually, with its own particular history and challenges. So those who collect evidence at the crime scene must have a very broad knowledge base when it comes to not only how to collect evidence, but also how evidence is processed at a crime scene (Saferstein 2004).

The examination of physical evidence is undertaken for two reasons: identification or comparison. Identification provides a substance’s chemical or physical identity; comparison is the process through which it is determined whether or not two or more objects have a common origin (Saferstein 2004).

The following is a list of common types of physical evidence found at crime scenes.

Although this list is comprehensive, it is not exhaustive. Common physical evidence includes blood, semen and saliva, documents, drugs, explosives, fibers, fingerprints, firearms and ammunition, glass, hair, impressions, organs and physiological fluids, paint, petroleum products, plastic bags, plastic, rubber and other polymers, powder residues, serial numbers, soil and minerals, tool marks, vehicle lights, and wood and other vegetative matter. Those who collect evidence must be familiar with the many different types of processing and packaging associated with the previous types of evidence.

Digital Evidence

With current technological advances, crimes nowadays are often committed with the use of technology. In these cases, in addition to physical evidence as identified earlier, digital evidence is left at crime scenes, ready to be collected. Digital evidence is “any data stored or transmitted using a computer that supports or refutes a theory of how an offense occurred or that address critical elements of the offense such as intent or alibi” (Casey 2004, 12). Unlike traditional physical evidence, police are not as familiar with digital evidence and often overlook it at the crime scene, or sometimes are aware of its existence but are unable to process it due to insufficient knowledge and lack of training. As was with the case of DNA, police must become more familiar with digital evidence in order to successfully solve crimes of the future.


Criminal investigation is a complex and tedious process that requires a certain knowledge base, skills, and attention to detail. This process is perhaps the single most important action performed by police because it starts the action of a case in the entire criminal justice system. Criminal investigation varies from agency to agency based on numerous factors. Regardless of the variation, each case must be treated individually while simultaneously adhering to consistent standard policies and procedures in order to facilitate the solving of crimes and improvement of the quality of life in contemporary society.

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