Collection of Forensic Evidence: Tools and Techniques

By Sahil Tandon, Symbiosis Noida

 Editor’s Note: This article discusses the various tools and techniques for collection of forensic evidence from a crime scene.

INTRODUCTION

Forensic science provides evidence to resolve legal issues through the application of scientific principles. Sometimes called simply forensics, forensic science encompasses many different fields of science, including anthropology, biology, chemistry, engineering, genetics, medicine, pathology, phonetics, psychiatry, and toxicology. Forensic evidence consists of all the physical objects that can be observed by the five human senses and analyzed regarding their relevance to the events that occurred at a crime scene. Any physical item can be a source of information that assists the investigator in reconstructing the sequence of occurrences. [1] The related term criminalistics refers more specifically to the scientific collection and analysis of physical evidence in criminal cases. This includes the analysis of many kinds of materials, including blood, fibers, bullets, and fingerprints.

Forensic scientists often present Expert Testimony to courts, as in the case of pathologists who testify on causes of death and engineers who testify on causes of damage from equipment failure, fires, or explosions.[2] Modern forensic science originated in the late nineteenth century, when European criminal investigators began to use fingerprinting and other identification techniques to solve crimes. As the field of science expanded in scope throughout the twentieth century, its application to legal issues became more and more common. Because nearly every area of science has a potential bearing on the law, the list of areas within forensic science is long. The Scientific Analysis Section has seven divisions: Chemistry Toxicology, DNA Analysis/Serology, Elemental and Metals Analysis, Explosives, Firearms-Toolmarks, Hairs and Fibers, and Materials Analysis.

The Latent Fingerprint Section examines evidence for hidden fingerprints, palm prints, footprints, and lip prints. Forensic engineers provide courts with expertise in areas such as the design and construction of buildings, vehicles, electronics, and other items. Forensic linguists determine the authorship of written documents through analyses of handwriting, syntax, word usage, and grammar. Forensic anthropologists identify and date human remains such as bones. Forensic geneticists analyze human genetic material, or DNA, to provide evidence that is often used by juries to determine the guilt or innocence of criminal suspects. Forensic phoneticians deal with issues such as the validity of tape-recorded messages, the identification of speakers on recorded messages, the enhancement of recorded messages, the use of voiceprints, and other aspects of Electronic Surveillance. Impression evidence can be generally defined as “objects or materials that have retained the characteristics of other objects or materials through direct physical contact”.  Many forms of impression evidence are encountered in forensic science such as fingerprints, footwear impressions, tyre marks or tool marks. These impressions are recorded by photography.

LITERATURE REVIEW

Bonnie. J Richard (2011) This paper explains Howard Zonana‟s contributions of the field over three decades. He is the voice of psychiatry in the law, and interpreter of law to the colleagues in psychiatry. He offers provisional impressions of the collective accomplishments under three themes – expertise, influence and integrity. Firstly, he has established and nurtured the expertise and authority of forensic psychiatry, which has become increasingly evidence-based and reflects a prudent sense of humility. Second, he has a significant influence on the design and daily application of mental health law in both criminal and civil spheres. Finally, he has nurtured and protected the ethical integrity of the profession in the face of ever-increasing challenges.

Kaye H. David (2003) This paper establishes that the Forensic scientists are concerned with “individualization. They often presume that features such as fingerprint minutia are unique to each individual. In at least two cases, the government of the United States has successfully relied on an unpublished statistical study prepared specifically for litigation to demonstrate the uniqueness of fingerprints. This article suggests that the study is neither designed nor executed in a way that can show whether an individual’s fingerprint impressions are unique.

Smith B. Michael (2009) This paper suggests that because footwear impressions are found at virtually every crime scene, footwear impression evidence often provides an important link between the suspect and the crime scene. This information may place the suspect at the crime scene or eliminate the suspect as having been there. Although crime scene technicians still fail to recognize the importance and value of footwear impressions as physical evidence. Often, impressions are overlooked, improperly collected, or not collected at all.

Warrington Dick (2007) From the overview, you can see that there are a number of excellent products out there that allow you to recover detail so fine that you can see everything. Test the various products available. Once you figure out which ones you like to use best, be sure to add them to your crime scene kit. Suspects often leave important evidence throughout crime scenes: tire tracks, footprints, tool marks, extruder marks on different casings, etc. Casting can preserve this impression evidence for comparison work and analysis at the lab. Since this evidence can be crucial for your court case, you need to know the proper way to handle it.

Moriatry Campbell Jane, Saks J. Michael (2006) This article exhaustively but briefly reviews the variety of forensic sciences and the bases on which they rest – drawing a major distinction between those that assert the ability to individualize crime scene evidence to its one and only and those which do not assert individualization. This article also assumes that judges most of the time will admit most such evidence regardless of the commands of the Daubert trilogy and the rules of evidence, and offers practical suggestions about what judges might do to improve their management of such testimony and to protect fact finders from the most misleading claims and unsupportable opinions, while still admitting the testimony into evidence.

RESEARCH QUESTIONS

The purpose of the research is to find out answers to the questions by application of the procedures set out by the experts.

  1. Where can the footwear evidence be found?
  2. Who collects and examine the impressions?
  3. What is the admissibility of such impressions found?
  4. What is the procedure of collecting the footwear evidence found at the crime scene? 

FINDINGS AND CONCLUSION

Foot Prints

Forensic footwear evidence can be used in legal proceedings to help prove that a shoe was at a crime scene. Footwear evidence is often the most abundant form of evidence at a crime scene and in some cases can prove to be as specific as a fingerprint. Initially investigators will look to identify the make and model of the shoe or trainer which made an impression. This can be done visually or by comparison with evidence in a database both methods focus heavily on pattern recognition and brand and logo marks. Information about the footwear can be gained from the analysis of wear patterns that are dependent on angle of footfall and weight distribution. Footwear evidence should be one of the first considerations at the crime scene. Once the first officers on the scene have made the scene safe, it should then be secured for the crime scene investigator. The secured area should be marked off large enough to include any possible footwear impressions that may be leading to and away from the area. This officer securing the scene should pay careful attention not to leave his footwear impressions around the scene. Footwear evidence can be found at almost all crime scenes in two forms, impressions and prints. The techniques in recording such evidence may be different, but the search is basically the same. Always use a methodical and planned method of searching.

There are four basic methods of recording footwear impressions at the crime scene.

  1. Photography
  2. Documentation/Sketching
  3. Casting
  4. Lifting

Whether the impressions are indoors or out, they should be photographed, documented, lifted and/or cast. A photograph or lift differs from a cast in that it is a two-dimensional reproduction of a print, just as a fingerprint lift. A cast is a three-dimensional structure, which can provide a positive reproduction of the footwear. Some impressions may only lift in partial and others do not lift at all, so always attempt to photograph the prints first. If the footwear is a visible print on an item that can be retrieved from the scene to the laboratory, then this should be the method of choice. It is much easier to work on the evidence under controlled conditions than to try collecting the footwear at the crime scene, but in some cases this is not possible. There are many lifting applications on the market that have been accepted for years. Adhesive paper or contact paper can be placed over the footwear print in dust or very light dirt.

This lifting method works by placing the adhesive paper or contact paper, adhesive side down, over the impression in dust or light dirt and smoothing over. This will allow the impressions to be transferred to the adhesive side of the paper. Once this is done the paper is then peeled off the impression and photographed. The paper can be treated with a mixture of 0.05 grams of crystal violet to 500 ml. of distilled water which stains the footwear impression, but produces a reversed image when collected. Once this is completed a piece of clear acetate is placed over the print in order to preserve it for impounding and later examination purposes. Latent fingerprint powders and lifting tapes can be used on various surfaces for contrast and recovery.[3]

Many latent footwear impressions can be located with the oblique lighting technique. Once found they can be difficult to photograph, but latent fingerprint powders can be used to build contrast for easy photography. This procedure is performed in the same manner as if you were dusting for latent fingerprints. Once the prints have been developed and photographed, the recovery process is the same using fingerprint lifting tapes and suitable contrast backgrounds to place the lift on. Never cover an impression with tape to reserve it until after the completion of the photographs. The tape will only obliterate the print and make subsequent enhancement difficult. Place the tape over the impression only after all other methods of enhancement have been exhausted. Make sure the footwear evidence was not placed in dust, as there may be more suitable methods of collection.

Whenever possible, impression evidence is collected as is and submitted to the laboratory for examination. For shoeprints and tire tracks that cannot be picked up, various lifting techniques are used to recover the evidence. These include:

Adhesive lifter – a heavy coating of adhesive lifts the imprint from smooth, non-delicate surfaces such as tile or hardwood floors, metal counters, etc. It is usually used in conjunction with fingerprint powders.

Gelatin lifter – a sheet of rubber with a low-adhesive gelatin layer on one side that can lift prints from almost any surface, including porous, rough, curved and textured surfaces. It is less tacky and more flexible than an adhesive lifter, allowing it to pick up a dusty shoeprint on a cardboard box, for example, but not tear the surface of the box.

Electrostatic dust-print lifting device – a tool that electrostatically charges particles within dust or light soil, which are then attracted and bonded to a lifting film. This method is best for collecting dry or dusty residue impressions on almost any surface, even the skin of a cadaver. Comparison samples are usually taken from suspects or suspect vehicles. Shoe samples should be packaged to avoid cross-contamination and tire samples should remain on the vehicle.

Crime Scene Footwear Evidence – Footwear evidence can be found in two forms, impressions and prints. The impression is normally described as a three-dimensional impression, such as an impression in mud or a soft material; and the print is described as a print made on a solid surface by dust, powder, or a similar medium. Footwear evidence, as well latent fingerprint evidence, is classified into three categories of crime scene prints:

  1. Visible Prints
  2. Plastic Prints
  3. Latent Prints

The Visible Prints: A visible print occurs when the footwear steps into a foreign substance and is contaminated by it, and then comes in contact with a clean surface and is pressed onto that surface. This print can be visibly seen by the naked eye without any other aids.

The Plastic Prints: Plastic prints are impressions that occur when the footwear steps into a soft surface, such as deep mud, snow, wet sand, or dirt creating a three-dimensional impression. This type of impression should be photographed and then cast. These types of impressions are three-dimensional because they allow the examiner to see length, width, and depth.

The Latent Prints: Latent prints are the most overlooked print and are generally found on smooth surfaces. They can be developed the same way latent fingerprints are. This type of print needs a variety of powders, chemicals and even forensic light sources to make it visible in order to properly be collected. In most cases these prints should also be photographed prior to any recovery process.[4]

Admissibility of Footwear Evidence

“The role of the expert witness is not to determine guilt or innocence, but rather to assist the court in determining what weight is to be placed on technical evidence entered which without assistance could not be interpreted properly.” (Cassidy, 1980) The basic premise involved in crime scene photography is that the photographs are a true representation of the scene as the investigator initially observed it. Nothing will cause evidence to be tossed out of court faster by defense attorneys than no photographs of the footwear evidence prior to the crime scene investigator placing a scale in the photograph or not following proper procedures.

Crime Scene Investigators are considered to be expert witnesses in the investigation of the crime scene. Only the court determines the expert witness. The court will weigh the qualifications, experience, and demeanor of the investigator carefully every time that he/she appears. The expert witness is allowed to give an opinion on any relevant issue that is within the scope of their expertise. Once the footwear evidence has been entered into evidence, the Footwear Examiner will take the stand to testify as to the examination or comparison procedures. Never allow yourself to become caught up in testifying to an examination or the comparison of footwear evidence unless you have been properly trained and possess the experience, qualifications and training of a footwear examiner.[5]

WHO CONDUCTS THE ANALYSIS?

Evaluation and comparison of impression evidence should be performed by a well-trained footwear and tire track examiner. Typically these professionals have received extensive training on footwear and tire manufacturing, evidence detection, recovery, handling and examination procedures, laboratory and photography equipment and procedures, courtroom testimony and legal issues, and casework.

Evidence Submission and Examination

Ideally, the suspect’s shoes are submitted to the lab along with the collected evidence. Examiners will use the submitted shoes to make test standards, impressions of a known source, which can then be compared to the collected evidence. This is usually done using transparency overlays or side-by-side comparisons. In some cases, an investigator may be asked to submit shoes of other individuals for exclusion purposes, such as from a cohabitant of a home or from a first responder to a crime scene.

Tools and Techniques

During the examination and comparison, examiners use tools such as dividers, calipers, special lighting and low magnification. Examiners measure the various elements within the tread design as well as the length and width of the impressions, and then compare those measurements to what is seen in the crime scene print or impressions. Low magnification and special lighting are sometimes used to determine if various characteristics are accidental or something that was created during the manufacturing process. Examiners perform side-by-side comparisons by placing the known shoe or tire alongside the crime scene print so that corresponding areas can be examined. Test prints are also compared to the crime scene print. Digital images on double or triple computer monitors can also be used during the comparison.

CONCLUSION

“Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will  serve as silent evidence against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects – all these and more bear mute witness against him. (Paul,Kirk)[6]

The most important aspect of evidence collection and preservation is protecting the crime scene. This is to keep the pertinent evidence uncontaminated until it can be recorded and collected. The successful prosecution of a case can hinge on the state of the physical evidence at the time it is collected. The protection of the scene begins with the arrival of the first police officer at the scene and ends when the scene is released from police custody.

The first person to note this condition was Dr. Edmond Locard, director of the world’s first forensic laboratory in Lyon, France. He established several important ideas that are still a part of forensic studies today. Locard’s exchange principle states that when a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur. The second part of Locard’s principle states that the intensity, duration, and nature of the materials in contact determine the extent of the transfer. More transfer would be noted if two individuals engaged in a fistfight than if a person simply brushed past another person.

Edited by Hariharan Kumar

Bonnie J. Richard, Howard Zonana and the Transformation of Forensic Psychiatry University of Virginia School of Law, (2011).

Kaye H. David, Center for the Study of Law, Science, and Technology, Arizona State University, Questioning a Courtroom Proof of the Uniqueness of Fingerprints (2003).

Moriatry Campbell Jane, Saks J. Michael, Duquesne University – School of Law, Forensic Science: Grand Goals, Tragic Flaws, and Judicial Gatekeeping (2006).

Smith B. Michael, FBI Laboratory
 Quantico, Virginia, The Forensic Analysis of Footwear Impression Evidence (2009).

Warrington Dick, Lynn Peavey Company, USA, Impression Evidence (2007).

Naples, V., & Miller, J. (2004). Making tracks: The forensic analysis of footprints and footwear impressions. Anat. Rec., 279B(1), 9-15. doi:10.1002/ar.b.20025

Forensic Science. (2008). The free dictionary by Farlex. America. Retrieved from http://legal-dictionary.thefreedictionary.com/Forensic+Science

Fuller, J. (2015). Preserving Impression Evidence — Plaster Casts – HowStuffWorks. HowStuffWorks. Retrieved 15 March 2015, from http://science.howstuffworks.com/impression-evidence2.htm

Hilderbrand, D. (2007). Footwear, the missed evidence. Wildomar, CA: Staggs Pub.

Warrington, D. (2012). Impression Evidence: Building Your Case with Duplicate Evidence. Forensic Magazine. Retrieved from http://www.forensicmag.com/articles/2012/06/impression-evidence-building-your-case-duplicate-evidence

Crime scene & Evidences Encountered. (2013). Forensic Science Blog. Retrieved from http://sifs.in/blog/crime-scene-and-evidences-encountered

[1] http://onlinelibrary.wiley.com/store/10.1002/ar.b.20025/asset/20025_ftp.pdf;jsessionid=3D5D4CCB418A842EC7E55F9977928CFF.f02t03?v=1&t=i78t9x8d&s=73593f707f2b59aa606571b24e41ad6bcb638a33

[2] http://legal-dictionary.thefreedictionary.com/Forensic+Science

[3] http://science.howstuffworks.com/impression-evidence2.htm

[4] http://www.crime-scene-investigator.net/footwear.html

[5] http://www.forensicmag.com/articles/2013/03/collecting-impression-evidence

[6] http://sifs.in/blog/crime-scene-and-evidences-encountered/

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