Police Investigations in the Twenty-First Century


  • 1 Criminal investigations
  • 2 Collecting evidence for use in court
  • 3 Procedural law
  • 4 Rule of law in collecting evidence
  • 5 Search and seizure
  • 6 Search warrants
  • 7 Warrantless searches
  • 8 Interrogation and the Fifth Amendment
  • 9 The crime analyst and the criminal investigator

Learning Objectives for Chapter 5

  • 1 Understand the primary role of the police investigator
  • 2 Become familiar with the rule of law in collecting evidence of a crime
  • 3 Be conversant with the rules regarding search and seizure
  • 4 Gain a better understanding of when a warrantless search may be conducted
  • 5 Know the rules for interrogation of suspects
  • 6 Begin to appreciate the association between investigation and intelligence

Police patrols may be the primary crime control tactic of law enforcement. However, the second major tactic is investigation of reported crimes by detectives. While police patrols have been around since the beginning of police departments in America, the detective specialist in policing is of a more recent vintage. Not until around the beginning of the twentieth century did municipal police departments create the position of detective (Kuykendall and Koberg, 1982).

A number of factors converged near the end of the nineteenth century to bring about a demand for public police investigations of crime and criminals. Prior to that, citizens could hire private detectives—like those that worked for the Pinkerton detective agency. As the nineteenth century morphed into the twentieth century, fewer private citizens were able or willing to hire private detectives to find and recover stolen property (Langworthy and Travis, 1999). In addition, there was the public perception of a rising crime rate and the ineffectiveness of patrol officers in identifying and apprehending offenders. It might be said that the Keystone Kops—bumbling and incompetent police officers of the silent film era—of the early part of the twentieth century reflected one popular perception of the police in general. But it may have been the competency of the Pinkerton detectives, too, which provided the model of a police detective that led to the publics acceptance of the police department detective (Langworthy and Travis, 1999).


Detectives are responsible for criminal investigations. A criminal investigation is a lawful search for people and items useful in reconstructing an illegal act or omission and analyzing the mental state of the person or persons committing that act or omission (Weston and Lushbaugh, 2006).

The objective of criminal investigation is to determine truth as far as it can be discovered in any inquiry; it is a probing from the unknown to the known (Weston and Lushbaugh, 2006). Successful investigations are based not only on fidelity, accuracy, and sincerity in lawfully searching for the facts, but also on an equal faithfulness, exactness, and probity in reporting the results (Weston and Lushbaugh, 2006).

Criminal investigation means collecting evidence. Evidence is the only means by which the judge or the jury can be convinced of the truth or untruth of allegations and accusations made by prosecutors in a court of law. It is the job of detectives to collect all of the evidence and present it first to prosecutors and then to the court, but given this, the first item of concern is whether the evidence collected will be admissible in court. Admissibility depends on whether the evidence is relevant, material, and competent.

In the U.S. criminal justice system, the defendant is presumed to be innocent and it is the task of the prosecution to prove the case against the defendant beyond a reasonable doubt. The reality of this system is this: Accusations of crime must be supported in court by legally significant evidence. It is incumbent on the criminal investigator—the detective—to have a knowledge of evidence and its legal significance in order to be successful. In the final analysis, the success of an investigation depends on the evidence collected and its legal significance (Weston and Lushbaugh, 2006).

Rules of Procedure in Collecting Evidence

In a perfect scenario within the field of criminal justice, a crime is committed and the suspect is immediately caught, smoking gun in hand, and shortly thereafter offers a legal, signed confession of his guilt. However, this is not the way these scenarios get played out in reality. Rarely is the suspect even remotely in the vicinity of the crime, and the smoking gun? No smoking gun with his fingerprints on it. Instead, the “smoking gun” is usually a piece of physical evidence left behind at the scene.

Regardless of the evidence left behind at the scene, there are very well-defined rules of procedure that must be followed so that any evidence collected by the police can later be used in court. The Fourth Amendment to the U.S. Constitution is a brief amendment, but it has an important function in preserving the rights of citizens. The Fourth Amendment reads:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

(Hall and Ely, 2009, p. 413)

Once a criminal investigation has commenced, and a crime scene has been identified, the need for proper collection and maintenance of evidence related to that investigation is crucial to the achievement of a successful arrest and prosecution in the case. As Hess and Orthman (2010) put it, “a primary purpose of an investigation is to locate, identify, and preserve evidence—data on which a judgment or conclusion may be based” (p. 122). The proper collection of evidence will help to strengthen the case for the prosecution while eliminating any room for suggestion of a false arrest by the defense.

However, the collection of evidence cannot begin without the actual crime scene being located. The preliminary search of a location thought to be related to the commission of a crime aids in establishing proof that the scene was in fact linked to the crime itself. Once the scene is determined to be that of the actual crime, then the act of evidence collection begins.

Photographing the crime scene as it appeared, prior to the disruption caused as a result of a search for evidence, helps to maintain the integrity of its original condition as it appeared just after the crime was committed and before the suspect had fled. The image of an undisturbed crime scene is a powerful piece of evidence that a jury can use when evaluating the mindset of the criminal—why and how they committed the crime. Also, pre-search photographs of a crime scene can aid in establishing the condition and placement of evidence prior to the evidence being collected and secured.

Once the scene is secured and photographed, the placement of markings next to items of evidence being seized helps to establish, by number, which item was found first and the location of each item as it pertains to its collection. An evidence log is also needed to chronologically log the collection of each piece of evidence by date, time, number of item, and location. Photographing the item once it is marked—and prior to its collection—helps to aid the prosecution when they attempt to piece the scene together for a jury.

After marking, logging, and photographing evidence, the next step is to physically collect the evidence for examination and testing. Following established protocol when collecting evidence helps to eliminate any suggestion that the item seized was contaminated or collected improperly. In addition, abiding by the proper method of collection helps to maintain the integrity of any laboratory tests that are meant to establish a connection between the suspect and the item seized.

The final step in the process of crime scene investigation has to do with after-search photographs. These photographs are intended to document the crime scene as it appeared once the search and seizure of evidence was completed. It aids the defense against a criminal accusation if it can be shown that property left behind was intentionally damaged or that important evidence was ignored intentionally or through negligence. The “before,” “during,” and “after” photographs of a crime scene help to complete a necessary visual aid, not only for investigators to refer to as they continue on in their investigations, but also for any judge or jury to ponder as a point of reference when connecting an item to the location at which it was found.

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