The Daubert-Kumho Test

The DAUBERT-KUMHO Test happens to be the new test of expert testimony. The trial Judge is to determine whether or not the Expert Witness has expounded upon the stature of scientific knowledge. It consists of four factors

1. Testing of the theory

2. Review of peers of the technique

3. Potential rate of error

4. The theory of technique generally accepted

References:

Garland Norman (2006) Mc Graw Hill, Criminal Evidence Fifth Edition 

Toxicologist

The Toxicologist is known as a doctor or professional in the field of identifying the presence of drugs in a subject.  They work for hospitals, laboratories, and police departments. You must have a thorough understanding of how internal organs produce enzymes, fluids and antibodies to be a Toxicologist.

Many tests can be performed that allow the toxicologist to identify whether or not drugs are present in the subjects system.  The three main tests are Thin Layer Chromatography (TLC), Gas Chromatography (GC), and Enzyme-Multiplied Immunoassay Technique (EMIT).

Gas Chromatography (GC)

This type of machine identifies illicit drugs by using stationary liquid to produce gas that rises into the surrounding environment. The sample is injected into a heated chamber, a constant stream of nitrogen gas flows through the injector forcing the sample through a series of seven columns that has a thin film of liquid present. The columns separate the gases and then the gases enter the detector that activates the recorder producing a recording that traces peaks and valleys based on a timed scale that identifies the concentration of drugs.

Thin Layer Chromatography (TLC)

A gel coated plate is spotted with a droplet of a blood sample from a suspect. Then the plate is placed into a closed chamber that is filled with a rising solvent. The greater the affinity of the substance the greater the speed it will travel up the plat. Then the plate is analyzed and compared with other plates that have been tested with substances similar to the one that has been tested.

Enzyme-Multiplied Immunoassay Technique (EMIT)

Enzyme –Multiplied Immunoassay Technique (EMIT) can be used for testing urine for a number of illicit drugs, the EMIT process consists of adding the antibody of the drug that the subject is being tested for.

Tests for alcohol represent a large number of incidents traffic and violence related crimes. The Toxicologist must test for alcohol by performing a breathalyser test, blood test, or urine test. The breathalyser is a well known device that is used frequently by Police Departments , it is almost a fail safe way to measure the amount of alcohol in a person’s breath and blood stream.

The Electronic Breathalyser

The Breathalyser test works by a chemical reaction that detects ethanol which is found in alcohol. When a subject blows through the tube of a Breathalyser test the chemical reaction detects ethanol in the air and compares it to a non toxic level. The chemicals used are sulphuric acid, silver nitrate, potassium sulphate and chromium sulphate. Sulphuric acid forces the alcohol to dissolve. The chromium sulphate and potassium sulphate react to the alcohol thus producing a small power surge. The silver nitrate speeds the reaction up for better charge detection. The electricity is then compared to a base reading and displayed on the screen for how much over or under the illegal rate of alcohol the subject is. 

References

Fisher, Berry A. (2004) CRC Press, Techniques of Crime Scene Investigation

Saferstein Richard (2007) Pearson Prentice Hall, Criminalistics, An Introduction To Forensic Science Tenth Edition 

Live strong.com (2010), How Does the Breathalyser Test Work? From source http://www.livestrong.com/article/30109-breathalyzer-test-work/

Altering A Crime Scene Photograph

I can only think of several reasons for changing a photograph one is to create a stitch or panorama of a tire track or a foot prints. Another reason to change photographs is to accurately scale the photograph film to make sure it is scaled properly. In both these instances a crime scene investigator would have to use Adobe Photoshop C3 to make the correct changes.

To maintain a fair and accurate depiction of the crime scene you must not change photographs to delete or add items to the photograph that may be misleading. You also need to be able to take photographs that are in the same lighting as the witness sees them. This means that if a witness depicts a crime scene in midday to take photographs that are near midday to depict the crime scene.  A crime scene investigator must always take photographs that are near the accuracy of the size of the actual photograph that they are trying to depict. Other inconsistencies are to accurately depict the size and depth of rooms and hallways photographed by the camera. If these standards are not meet they may disqualify the photographic evidence and have it thrown out of court.

References:

http://www.theiai.org/guidelines/swgit/swgde/swgde_swgit_proficiency_test_document_v1-1.pdf

Criminalistics (An Introduction To Forensic Science) Ninth Edition Author: Richard Safertein Ph.D.  Editor: Pearson Prentice Hall Copyright 2007

Depth of Field

Depth of field allows you to photograph the whole subject matter while keeping the actual focus on the single object. Many photographs will not allow you to take pictures of a single object with distractions in the way moving people, cars, trees, bushes, other photographers, it helps to find a good angle to take photographs from afar while keeping your objective centered. Some of the best pictures use depth of field for objects that either do not fit within regular lens size or need modification to view the whole subject matter. Magnification of the lens plays a big role in focusing  the camera to have depth  of field, another factor of depth of field are the f /stop setting they allow you to view the photograph in the correctly  lighting. Crime Scene investigators should not leave any object out of focus this technique is only used for photographers that take pictures for leisure or sales purposes. All photographs for Crime Scene Investigator must be in focus and directed to the subject matter. 

References:

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

http://www.photoxels.com/tutorial_dof.html

http://www.photoaxe.com/depth-of-field-photography-tutorial-part-3/

Manipulation of Photographs 

Manipulations are described by adding or deleting details to the photograph. A photograph with the subject centered cannot be edited to delete prudent items from the background. The subject is not to be changed or altered to depict a view of the photograph that was not present when the photograph was first taken. The SOP (Standard Operating Procedure) begins with SWGIT (Scientific Work Group of Imaging Technology) they regulate what changes are acceptable for crime scene investigation photographs that are presented at trial. Manipulations that alter the subject by editing the photograph or deleting items from the photograph that are present in the original copy are not admissible in trail.