Crime Scene Evidence - Convictions Are Rare Without Physical Evidence From the Scene

Sensational homicides have populated the National news of late, and crime scene evidence seems to play a key part in many courtroom decisions. Numerous TV "Cop Shows" draw bigger and bigger audiences as the viewing public develops an insatiable appetite for the' blood and guts" of crime scene investigation.

Crime scene investigation (CSI) includes some basic methods that include forensic applications, photography, chemistry, physics, mathematics and just plain common sense. "How to Become a CSI" is a fast-growing industry among institutes of higher learning offering on-line diplomas and degrees in the discipline.

One fact is certain: No two crime scenes are very much alike.

Crime scene investigation must follow an orderly protocol-otherwise physical evidence may be misunderstood, mishandled, or missed altogether. The basics steps taught to crime scene investigators by many educational sources include, but are not limited to the following steps:

1. Protect Life and Property. The first responding officer(s) must take the steps necessary to protect life and property. First aid is rendered to the injured and aid in the form of emergency medical teams, crash-rescue units, fire departments and backup officers are summoned.

2. Secure the Scene. Officers must take steps to prevent damage to, or disruption (contamination) of the scene. Many experts in this field state that more harm is inflicted on crime scenes by the presence of law enforcement officers than from any other source. The first officers on the scene must make a quick determination of what constitutes the boundaries of the scene, and will then take steps to protect this area. This is where the inevitable "Yellow Crime Scene Tape" is introduced into the crime scene. Sentries must be placed at all possible points of entry and access will be denied to all not having a legitimate reason for entering the area.

3. Brief the Investigators. Except in very small law enforcement agencies-where the first responders may also wear the hats of crime scene investigators, the first responders will brief those on hand who will assume control of the scene and perform evidence search and collection. This briefing includes any observations made by initial officers and will relay statements made by by-standers, witnesses and victims.

4. Conduct a Walk-Thru. The walk-thru is a time spent making visual observations throughout the scene. Physical evidence can be in plain sight (weapons, spent-shell casings, blood, impression evidence (hand and footprints), etc. The investigator will make notes as potential crime scene evidence is revealed. The walk-thru skirts the perimeter of the areas where obvious physical evidence resides. All the while, the investigator is conscious of the fact that a great deal of evidence may be present that is not in plain view or is invisible in nature. Thus he must avoid walking through areas that may harbor footprints in dust, weak or invisible bloodstains or blood spatter and latent fingerprints.

5. Recording the Scene. Recording the scene most often begins with CSIs preparing a rough sketch of the area. Locations of furniture and other building contents are included as well as apparent items potentially useful as crime scene evidence. Outdoor scenes present different challenges so nearby vegetation, trees and similar fixed and moveable objects are sketched. Next comes photography. Overall, wide-angle photos record the scene prior to any efforts to locate physical evidence. Medium distance photos follow that show relative positions of evidential items with regard to each other, and then close-ups record specific items. Many agencies also use video to supplement still photographs. As far as human nature is involved, a jury's rapt attention is often stronger when videos are used to depict the scene. Video provides a sense of actually being at the scene for jurors.

6. Processing the Scene for Physical Evidence. This is the nitty-gritty phase of the investigation. Often, specialists skilled in locating and recovering dust impressions are joined by latent fingerprint technicians who will ply their expertise. In violent crime scenes, a blood spatter analyst will go to work.

7. Collecting the Physical Evidence. It is one thing to locate potential evidence, and it is another to gain the usefulness this evidence may possess. Collecting techniques may include an electrostatic dust print lifting system, superglue fuming of various items in order to reveal invisible latent fingerprints, and there is also a mix of physics and geometry when analyzing and recording blood spatter.

8. Packaging and Transporting Collected Evidence. Much of the evidence collected at a crime scene is very fragile in nature. This evidence may be damaged by handling and the packaging method, and it may deteriorate or "spoil" due to improper storage. Physiological fluids, and their potential for providing DNA profiles, are especially fragile and easily susceptible to damage or deterioration.

While some TV shows run through all of the above steps in just 45 minutes or so, it is apparent that investigating a crime scene can take many hours or even several days from start to finish.

The National Institute of Justice has performed in-depth research into the "CSI Effect." This is based on the premise that juries are being conditioned to expect to see the very same techniques used by TV actors to be employed by the real-life cadre of CSIs. What the general public expects to see are scientific principles and equipment resulting in "Slam-Dunk" prosecutions, while failing to comprehend that many of the techniques depicted on TV require extensive, virtually unlimited budgets to accomplish. See The NIJ video.

Most law enforcement CSIs are adapting to the budget crunch, and they are still able to bring the guilty to justice through their dedication and perseverance-despite the lack of sufficient funding.

Many law enforcement agencies have been forced to limit training and are coming to recognize that a great deal of specific crime scene training is available to them at no cost. The CSI Tech Blog offers specific training in Crime Scene Evidence disciplines, and it is a trusted source for learning the many techniques and procedures needed by today's crime scene teams. Visit CSI Tech Blog

Expert Author Don Penven is a freelance writer and professional photographer based in Raleigh and Morehead City, NC,

Crime Scene Evidence - The Value of a 3D Laser Scanning Survey

After the commission of crime, investigators are called to the scene to gather evidence that will lead to the perpetrator. But in the case of crimes that require complex evidence gathering, such as murders, investigators rarely have as much time as they need to gather evidence. Because recreating a crime-scene can play an essential role in solving crimes, even the position of seemingly inane crime scene objects can have a significant impact on how the commission of a crime is eventually interpreted, which can in turn play a significant role in identifying the right suspect and eliciting a confession.

Traditionally, investigators make written notes and take photographs of a crime-scene, which rarely results in enough evidence to accurately recreate it. One reason why traditional crime-scene evidence makes it difficult to recreate crimes is that investigators are under pressure to record information as quickly as possible, which increases the chance that critical elements of the crime will be overlooked. However, even if investigators could take as much time as they pleased, the fact that most crimes occur in residences, public buildings or public spaces makes it impossible to preserve a crime scene for more than a few hours.

In the past, police departments had no answer to these problems. But today, many police departments put these problems to rest by using laser scanning-also referred to as 3D laser scanning-to record the objects and distances of a crime-scene. 3D scanning is commonly associated with the engineering and manufacturing industries, where it is used to model new parts and objects and trouble shoot existing parts and objects to correct imperfections. Unlike traditional surveying methods, a 3D laser scanning survey results in accurate data gathering in as little as one surveying session, making it ideal for gathering information from time sensitive crime scenes.

When a laser scanner is used to scan a crime-scene, it records the scene's spatial data to a computer that is contained within the scanner. Then the scanner is connected to an external computer where the data is downloaded. After being downloaded, the data can be expressed in a variety of forms, but police departments express the data in solid CAD models, which are highly editable and allow the crime scene to be viewed from various vantage points. In addition to allowing investigators to record the objects and distances of a crime scene, 3D scanning also allows investigators to create crime scene animations to judge bullet trajectory, the path of falling objects or recreate a struggle between the perpetrator and the victim. In addition to serving as a valuable investigative tool, crime scene animations can be presented in court as a valuable element in jury persuasion.

In my research on laser scanning, I've discovered the value of 3D laser scanning to crime scene investigations.