CHAPTER 3 CRIME SCENE INVESTIGATION

• Jurisdiction: United States

Chapter 3 Crime Scene Investigation Overview

Locard's Principle says that every person who comes in contact with an object or person will make a cross transfer of evidence that will identify him. This principle is why crime scene investigators examine a crime scene in detail. Forensic evidence must be collected carefully and following all laws in order to be admitted in trial. The process requires investigators to carefully document all evidence and to remain objective. An expert who testifies about the crime scene may rely on notes or drawings prepared by others, so long as they do not contain opinions or conclusions.

One of the objectives is to link forensic evidence to suspects. Forensic evidence may demonstrate either class characteristics or individual characteristics. Class characteristics will be those that will "include" the suspect, such as the same shoeprint, but individual characteristics are those that can conclusively identify a suspect, such as DNA. Both investigators and juries need to be aware of the difference.

Chain of custody requires that evidence be properly controlled and accounted for in order to be admissible at trial. Some courts refuse to admit evidence where there is a break in the chain of custody. Others admit the evidence, but allow the defendant to argue that the jury should take the break in the chain and possible tampering into consideration in their deliberations.

Courts are now mindful that juries may expect forensic evidence and have tried to avoid prejudice by questioning in voir dire and by jury instructions.

An expert may testify based on crime scene drawings or sketches prepared by someone who is not in court, unless they contain any conclusion or opinion, in which case the Confrontation Clause would require the presence of the investigator who wrote the report.

Counsel must carefully select and prepare the forensic expert in order to persuade a jury that the expert's opinion is correct. Some believe that the criminal justice system favors the prosecution in the area of expert testimony, as states have forensic laboratories and technicians to test and testify, whereas defendants must hire expensive experts to evaluate or contest the state's evidence. At least one court has held that failure to request a more expensive, "better" forensic expert constitutes "ineffective counsel," which may warrant reversing a conviction.

Chapter Objectives

Based on this chapter, students will be able to:

1. Define Locard's "Exchange Principle" and how it affects the processing of crime scenes.
2. Explain basic steps involved in securing and investigating a crime scene.
3. Describe why investigators should get a warrant to search a crime scene.
4. Distinguish the difference between class and individual characteristics in evidence.
5. Explain the importance of maintaining a chain of custody.
6. Describe the challenges in the Grant case to chain of custody.
7. Tell how to find and prepare an expert witness.

How Forensic Evidence Is Processed

Forensic evidence is generally collected from the crime scene by investigators working for law enforcement. Therefore, it is critical that the original crime scene investigators do their job properly. Although the actors on CSI make investigating look simple and dramatic, it is not. The actors often wade into a crime scene before it has been blocked off and secured. They almost never get a warrant before searching. They pick up and hand around pieces of evidence. And then they go back to the lab and process the evidence themselves — all in one hour!

Whether conducted by local law enforcement or a highly specialized team of forensic scientists, the objectives of crime scene investigation are to recognize, preserve, collect, safeguard, interpret and reconstruct all relevant physical evidence at a crime scene.¹

Forensic processing frequently involves two important groups of people. The crime scene investigators on the scene are typically local police officers or members of a major crime unit of law enforcement officers who are trained to collect evidence and investigate crimes. In Connecticut, for example, the state maintains four major crime units that respond to all crimes involving police officers and any other crime scene if asked for help by local law enforcement. A number of the larger cities maintain their own crime scene units, but smaller towns do not. In the event that local law enforcement arrives on the scene and contaminates it in any way, this may impede the ability of the crime scene unit to process the scene. This was one of the claims made in the murder investigation of JonBenet Ramsey, which today is a cold case. This case is discussed in the chapter on Questioned Documents.

The second group is composed of laboratory technicians. These technicians typically do not travel to crime scenes to gather evidence, but instead test evidence in the laboratory. Some technicians began as law enforcement officers. Christopher Grice, for example, the fingerprint expert who identified Grant's fingerprint and testified to the match at trial, began as a detective in New Haven and is now a fingerprint expert at the Connecticut State Forensics Laboratory. Today, many forensic laboratories hire only graduates of forensic training programs, or individuals with degrees in the hard sciences.

In 2009, the NRC Report evaluated the scientific reliability of many forms of forensic evidence collected from crime scenes. It noted that crime scenes can be investigated by sophisticated teams or by a single investigator: "Crime scene evidence collectors can include uniformed officers, detectives, crime scene investigators, criminalists, forensic scientists, coroners, medical examiners, hospital personnel, photographers, and arson investigators. Thus, the nature and process of crime scene investigation varies dramatically across jurisdictions, with the potential for inconsistent policies and procedures and bias.... [T]here remains great variability in crime scene investigation practices, along with persistent concerns that the lack of standards and proper training at the crime scene can contribute to the difficulties of drawing accurate conclusions once evidence is subjected to forensic laboratory methods."²

Locard's Exchange Principle

This principle states that whenever two objects come into contact, there will be a mutual exchange of matter. This means that the suspect will leave something of himself at the crime scene and will take something of the scene away with him. Of course, these items may be microscopic, but the investigator's job is to find them. The investigator seeks to link the victim and the crime scene to a suspect and/or objects identified with the suspect.

On-Site Investigation

The steps in on-site crime scene investigation must be done in order:

1. Ensure that the victim is not present or in need of help.
2. Ensure that the scene is safe and no suspects are present.
3. Block off the scene.
4. Detain all witnesses. Establish a security log to document all people who come in and out.
5. Observe and take notes.
6. Determine if the scene is the primary or a secondary crime scene.
7. Photograph the scene; videotape the scene.
8. Draw a sketch of the scene and add to notes.
9. Collect evidence, bag it and seal it for transport to the lab.

When the crime scene is on private property, detectives should obtain a warrant rather than relying on the consent of the owner for the search. Consent can be revoked. A warrant ensures legal validity of the search. Although police can search legally without a warrant in emergencies or to prevent the immediate loss or destruction of evidence, the U.S. Supreme Court has reversed some convictions based on searches that took place without a warrant. In one such case,³ an undercover policeman entered the defendant's apartment during a drug raid and was killed. Police thereafter searched the apartment without a warrant over the next four days, and found bullets, drugs and other items entered in evidence at trial against the defendant. The court reversed the conviction, stating:

There was no indication that evidence would be lost, destroyed or removed during the time required to obtain a search warrant. Indeed, the police guard at the apartment minimized that possibility. And there is no suggestion that a search warrant could not easily and conveniently have been obtained. We decline to hold that the seriousness of the offense under investigation itself creates exigent circumstances of the kind that under the Fourth Amendment justify a warrantless search.

A sketch of the crime scene is essential to the process. The sketch indicates the scale of the crime scene, so that photographs then relate to their actual location and size. Photographs of small items are taken with a ruled scale in the photograph to indicate actual size. Videotape is an important tool because it can capture three dimensional views that otherwise cannot be seen later.

Investigators will review the scene to determine if it is the primary crime scene or a secondary crime scene. The primary scene is where the crime took place, whereas a secondary scene may be where evidence has been removed, or where a victim may have been taken. For example, if a murder victim is placed in an unnatural position, investigators will look for the original site of the murder. If there is no evidence of bloodstain or blood spatter, investigators may conclude the victim was murdered elsewhere.

Evidence such as blood-stained items must be bagged in paper rather than plastic. Plastic will cause wet items to decay and bacteria to grow. Wrapping paper, manila envelopes or paper bags allow the items to breathe. However, charred debris from a suspected arson must be stored in an airtight container to avoid evaporation of a possible accelerant. Each item must be packaged separately to avoid contamination, breakage, evaporation, scratching or bending.

Investigators search the entire scene...