FOOTWEAR EVIDENCE IN FORENSICS

Footwear track evidence can be very instrumental to the successful conclusion of a criminal investigation.Detailed examination of footwear impressions can help to link a specific piece of footwear to a footwear imprint as each shoe will have unique wear characteristics.

Photographing Footwear Evidence

Written by Dwane Hilderbrand

Taking quality examination photographs

When making quality examination photographs of the evidence prints, be sure to use the same numbered marker you used when you were showing the relationship of the print to the scene. In order for a footwear examiner to perform a quality examination, high-quality, close-up photographs are required. Since footwear evidence can come in two different forms—prints and impres-sions—the techniques of photography are slightly different. This can be easily obtained with a little time and patience. There are many types of cameras that are being used for crime-scene photo-graphy, ranging from 35 mm and 4 x 5 film cameras to digital cameras.

 Tire Tread and Tire Track Evidence: Recovery and Forensic Examination (Practical Aspects of Criminal & Forensic Investigations) 

After the selection of the camera and the film or digital media, you will need to select an appropriate scale that will be present in all the photographs. This is very critical in order to allow for enlargement from the negative or image to make an exact duplicate of size (1:1). When no scale is utilized in the photograph, the examiner has no idea what the size of the real impression is. It then becomes difficult for the forensic photographer to print 1:1 scale photographs for examination purposes.

Types of footwear evidence

Footwear evidence can come in at least 3 forms, footwear outsole impression evidence, footwear insole impressions and footwear trace evidence.

Footwear outsole impression

Footwear outsole impressions are impressions left on an object that was caused by contact with a piece of footwear. These can left on the ground or raised surface by persons treading over it, left on doors or walls by persons attempting to kick or climb over a wall or even left on other persons after being kicked or stomped on.

Latent footwear outsole impressions:

Latent impressions are caused impressions that are not easily visible to naked eye. Such prints can be on many different surfaces such as floor tiles, concrete or even carpet. Latent impression may not be easily visible to the naked eye and its detection may require the use of additional specialized light sources such as portable UV lighting. Recovery typically includes photography as well as lifting with “gel” or “electrostatic” dust lifters.

Footwear Insole imprints

Footwear insole imprints are imprints left in the inside of footwear caused by contact from the person’s foot. Analysis of the insole imprints can be used to link a person(s) to a piece of footwear.

Footwear trace evidence

Footwear trace evidence is trace evidence that is recovered from footwear. Types of trace evidence that could be recovered include skin, glass fragments, body hair, fibres from clothing or carpets, soil particles, dust and bodily fluids. 

The study of this trace evidence could be used to link a piece of footwear to a location or owner.

Detection of footwear evidence

Detection of impression in ambient lighting

Detection with forensic light sources

Detection with electrostatic lifting devices

Detection with chemical enhancement

COURSES IN FOOTWEAR EVIDENCE:

Bournemouth University: 3D Laser Scanning & Forensic Footwear Evidence

FEW LINKS:

Footwear Impression Evidence: Detection, Recovery and Examination, SECOND EDITION (Practical Aspects of Criminal & Forensic Investigations) 

Tire Tread and Tire Track Evidence: Recovery and Forensic Examination (Practical Aspects of Criminal & Forensic Investigations)Search Amazon.com for Footwear track evidence

Forensic Saliva Analysis

Body fluids, whether excreted or secreted, help our forensic experts compile detailed reports on sexual assaults, death, and the identification of attackers among other things.A forensic investigation can involve the analysis of body fluids, including saliva, for evidence of toxins and both prescription and illicit drugs.Saliva can be of forensic significance because traces of drugs that are circulating in the body can be present in saliva. The composition of the saliva accurately mirrors the proteins that are present in both the blood and the urine. Thus, testing of saliva, which is easier and less obtrusive than obtaining a blood or urine sample, can be used to reveal the presence of prescription and illicit drugs.

Saliva is presented as an alternative matrix in the establishment of drug abuse. The ultimate salivary concentration is determined by the route of administration, the salivary pH, the degree of plasma protein binding,and the physico-chemical properties of the abused drug. Since the saliva/plasma ratio can exceed 1, saliva might be a better analytical tool than blood during roadside testing of potentially intoxicated drivers

Virkler and Lednev add that Raman spectroscopy has great potential as just such a non-destructive tool. In 2008, the team reported that it could be used to identify bodily fluids at a crime scene but those experiments were carried out with just a single sample of each type of fluid. Now, the team has extended the work significantly to investigate the potential for spectroscopic differences among different “donors” of the same fluid.

The researchers have used near-infrared (NIR) Raman spectroscopy to obtain spectra for pure dried human saliva samples from several donors in a controlled laboratory environment. By applying principal component analysis (PCA) on the spectra they demonstrated that dry saliva is a particularly heterogeneous substance. However, the Raman spectra can be described as being a linear combination of a fluorescent background and three spectroscopic components.

Forensic Preliminary Testing for Saliva (amylase)

Phadebas tablet method

1. Place 50 ul of each described dilution from above into a

test tube.

2. Add 1.0 ml of water, and ¼ Phadebas tablet (cut with scalpel

or razor blade CAREFULLY). Add the ¼ tablet using

forceps, NOT fingers to handle/cut the tablet.

3. Vortex to mix thoroughly.

4. Incubate at 37C for 30 minutes.

5. Add .25 ml of 0.5 M Sodium Hydroxide to each tube to stop

the reaction.

6. Centrifuge for 5 minutes.

7. A transparent dark blue supernatant

LATEST!!- New Forensics Tool Can Determine a Person’s Age from a Spit Sample

Researchers at UCLA have figured out how to determine age to within five years from nothing more than a saliva sample. The method relies on a process called methylation, which is a chemical change to one of the four building blocks of a person’s DNA. Methylation changes as our bodies grow older, contributing to age related diseases. In extracting DNA from saliva samples from more than 100 test subjects, the team found that it could zero in on a person’s age within five years by looking at just two of the 3 billion blocks that make up the human genome–such is the strong correlation between methylation and age.

References:

1. Enotes

2. Sourcebook in forensic serology, immunology, and biochemistry

3. Scientific Protocols for Forensic Examination of Clothing (Protocols in Forensic Science)

4. Forensic Biology: Identification and DNA Analysis of Biological Evidence

Are you in the Right Flight??

Dexter- Has got his Blood Splatter Analysis done! What About You??…. Yes Guys! This is where blood takes flight and we as forensic scientist need to know the Direction of Flight- i.e The trajectory of a blood drop which can be established by its angle of impact and directionality angle.

Now you need to know the basics in Direction in Blood Splatter. Here are few terminologies:

Draw-Back Effect – Blood in the barrel of a firearm that has been drawn backward into the muzzle.

Drip Pattern — A bloodstain pattern which results from blood dripping into blood.

Expirated Blood – Blood that is blown out of the nose, mouth, or a wound as a result of air pressure and/or air flow which is the propelling force.

Flight Path – The path of the blood drop, as it moves through space, from the impact site to the target.

Flow Pattern – A change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object.

Forward Spatter – Blood which travels in the same direction as the source of energy or force which caused the spatter.

High Velocity Impact Spatter (HVIS) — A bloodstain pattern caused by a high velocity impact /force to a blood source such as that produced by gunshot or high speed machinery.

Impact Pattern – Bloodstain pattern created when blood receives a blow or force resulting in the random dispersion of smaller drips of blood.

Impact Site — That point where force encounters a source of blood.

Low Velocity Impact Spatter (LVIS) – A bloodstain pattern that is caused by a low velocity impact/force to a blood source.

Medium Velocity Impact Spatter (MVIS) – A bloodstain pattern caused by a medium velocity impact/force to a blood source. A beating typically causes this type of spatter.

Passive Drop (Bleeding) – Bloodstain drop(s) created or formed by the force of gravity acting along.

Point (Area) of Convergence – The common point (area), on a two dimensional surface, over which the directionality of several blood drops can be retraced.

Point (Area) of Origin — The common point (area) in a three dimensional space to which the trajectories of several blood drops can be retraced.

Projected Blood Pattern — A bloodstain pattern that is produced by blood released under pressure as opposed to an impact, such as arterial spurting

Angle of Impact: The steeper the impact, the more elliptical or elongated, the blood drop

For a complete list of bloodstain pattern terms, as recommended by the International Association of
Blood Stain Pattern Analysts. (IABPA), go to: http://www.iabpa.org/
These terms should serve as a guide, for those who work and teach in the field of Blood Stain Pattern Analysis