Crime Scene Investigation: A Guide for Law Enforcement

This guide is intended for use by law enforcement and other responders who have responsibility for protecting crime scenes, preserving physical evidence, and collecting and submitting the evidence for scientific examination. Physical evidence has the potential to play a critical role in the overall investigation and resolution of a suspected criminal act. Realization of this potential depends on actions taken early in the criminal investigation at the crime scene. Developments in technology and improvements in the analysis and interpretation of physical evidence recovered from crime scenes will place even greater importance on properly documented and preserved evidence. An important factor influencing the ultimate legal significance of this scientific evidence is that investigators follow an objective, thorough, and thoughtful approach. The goal of this process is to recognize and preserve physical evidence that will yield reliable information to aid in the investigation.

Physics and Forensics

Forensic science is rarely out of the news these days. Hardly a week seems to pass without reports of a criminal being convicted by DNA evidence extracted from a single hair, a flake of skin or a trace of blood or saliva found at a crime scene. Less well known, however, is the way in which forensic science has benefited from our ability to identify the presence of molecules in a sample using infrared radiation.

21st Century Crime Labs

Well-equipped and well-managed state and local crime labs are a critical element of a local agency?’s ability to solve crimes. However, although advances are being made in forensic technology, the nation?’s 350 crime labs often do not have the resources to acquire and apply these technologies.

50 Largest Crime Labs (2002)

The 50 largest publicly funded forensic crime laboratories in the United States employed more than 4,300 full-time equivalent (FTE) personnel in 2002 and had total budgets exceeding $266.6 million. These labs received more than 994,000 new cases, including over 1.2 million requests for forensic services during calendar year 2002.* The requests represented about half of all requests for forensic services handled by publicly funded laboratories nationally.

State Screening Laboratories and Forensic DNA Banks

The collection of blood specimens for disease testing, paternity testing, or forensic testing has grown enormously in the last quarter of the twentieth century. As biomedical technology advances, more and more testing will be performed on smaller and smaller sample sizes. Although tissue samples may be collected for a specific purpose, it is not unlikely for them to be used for other reasons. These large collections of human tissue samples have been a matter of concern for privacy advocates.

DNA and Forensics: The Silent Witness

  • Proper collection and storage of evidence important step for future testing by lab
  • Evidence is screened to ID biological stains
  • Comparison samples are essential to help draw conclusions about linkages to scene/evidence
  • PCR-based testing is fast, reliable, allows small stains/sample size
  • Applications of DNA include suspect cases, investigative/no-suspect (CODIS) cases, and post-conviction cases

Behind the scenes: Forensic Entomology

Forensic investigation is hardly an unknown field to the insurance industry. However, an area that seems to garner little attention in claim investigation procedures is forensic entomology – which could save insurers and insureds millions of dollars.

Bug investigations? You have to be kidding. But, as the following case study reveals, insects can reveal many secrets in the process of claims investigation.

PCR Amplification for DNA Fingerprinting

The objective of this experiment is to develop a basic understanding of DNA Fingerprinting. Students will analyze PCR reactions obtained from different suspects and compare them to a crime scene sample.

The Green Revolution: Botanical Contributions to Forensics and Drug Enforcement

Forensic botany encompasses many sub-disciplines, including plant anatomy, plant ecology, plant systematics, plant molecular biology, palynology, and limnology. Although the field of forensic botany has been recognized since the mid-1900’s, the use of trace plant material as physical evidence in criminal casework is still novel. A review of published forensic casework that used plant evidence is presented here. Cases include the analysis of wood evidence in the Charles Lindbergh baby kidnapping, the use of pollen in establishing the location of a sexual assault, and pollen analysis to determine the time of year for burial in a mass grave. Additional cases discuss the use of plant growth rates to determine the time of a body deposit in a field, the use of diatoms to link individuals to a crime scene, and plant DNA typing to match seedpods to a tree under which a body was discovered. NewDNAmethods in development for plant species identification and individualization for forensic applications are also discussed. These DNA methods may be useful for linking an individual to a crime scene or physical evidence to a geographic location, or tracking marijuana distribution patterns.

Forensic Science from Fingerprints to DNA

Every day, many crimes are committed in Australia. To solve these crimes effectively ?- so that criminals are brought to justice – the police need to work very efficiently, using as many techniques as possible. Science has become an essential tool for the modern police force. Originally, the word “forensic” meant anything relating to a law court. But today it refers to a whole new subject. Forensics or forensic science means using science to solve crime. But what exactly does a forensic scientist do?

Defining a New Forensic Discipline: Microbal Forensics

A number of bacteria, viruses, and fungi pose serious health concerns to humans, threaten the U.S. agricultural economy and food supplies, and/or affect the environment. The potential for use of any of these pathogenic agents as a biological weapon has been demonstrated (recently with Bacillus anthracis and many times in history), and further attacks cannot be ruled out. Microorganisms make particularly good weapons because pathogenic agents can be grown from a single organism or cell and often inexpensively. Moreover, it may be impossible to identify when very small amounts of such materials have been removed surreptitiously from a facility that is authorized to possess pathogens. Even the smallest amount can become a major threat.

A study in Infrared

The techniques are ideal for analyzing hair and fibers, paints and inks, tapes, greases, powders, and almost any other evidential debris left at a crime scene – from forged social security checks to condom lubricant on a murder-rape victim.

Two of these “visual” techniques, IR and Raman spectroscopy, provide both the power and understandability of “fingerprint matching” to the most esoteric chemical comparisons.

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