Fingerprints: The First ID

Fingerprints: The First ID
Fingerprints are the oldest and most accurate method of identifying individuals. No two people (not even identical twins) have the same fingerprints, and it is extremely easy for even the most accomplished criminals to leave incriminating fingerprints at the scene of a crime

Each fingerprint has a unique set of ridges and points that can be seen and identified by trained experts. If two fingerprints are compared and one has a point not seen on the other, those fingerprints are considered different. If there are only matching points and no differences, the fingerprints can be deemed identical. (There is no set number of points required, but the more points, the stronger the identification. Fingerprints can be visible or latent; latent fingerprints can often be seen with special ultraviolet lights, although on some surfaces a simple flashlight will identify the print. Experts use fingerprint powder or chemicals to set a print; they then “lift” the print using special adhesives.

The pioneer in fingerprint identification was Sir Francis Galton, an anthropologist by training, who was the first to show scientifically how fingerprints could be used to identify individuals. Beginning in the 1880s, Galton (a cousin of Charles Darwin) studied fingerprints to seek out hereditary traits. He determined through his studies not only that no two fingerprints are exactly alike, but also that fingerprints remain constant throughout an individual’s lifetime. Galton published a book on his findings in 1892 in which he listed the three most common fingerprint types: loop, whorl, and arch. These classifications are still used today

Rohypnol

Rohypnol
 
remains within the system for up to 7 days after administration. It is important that it is specifically requested that they do the tests for drugs otherwise it will be missed.
 
• Rohypnol takes effect within 20-30 minutes of administration and lasts up to eight hours.
 
• It acts as a sedative by inducing amnesia, relaxing the muscles, and slowing down psychomotor responses.
 
• If combined with alcohol, Rohypnol can increase the feeling of drunkenness and lower inhibitions.
Ketamine Hydrochloride
What is it?
 
• A legal drug sold as a veterinary sedative or hospital grade anaesthesia
 
• When used in humans the drug acts as a dissociative anaesthesia – leaving the user vaguely aware of, but comfortably detached from all bodily sensations
What are the effects?
 
• Delirium, Vivid hallucinations, Cardiac excitement, Mild respiratory depression, Confusion, Irrationality, Violent or aggressive behavior, Vertigo, Slurred speech, Delayed reaction time, Euphoria, Altered body image, Coma
How quickly does it affect and then leave the system?
 
• This depends on how it is ingested
 
• When taken orally or nasally the effects take 10-20 mins to be realised
 
• When taken intravenously the effects are instantaneous
 
• The effects last less then 3 hours and the drug is detectable in the system up to 48 hours after, depending on the method of ingestion
Gamma Hydroxy Butyrate (GHB)
What is it?
 
• Odourless, colourless liquid that acts on the central nervous system as a depressant/anaesthesia
What are the effects?
 
• Euphoria, Amnesia, Intoxication, Drowsiness, Dizziness, Nausea, Visual hallucinations
How quickly does it affect and then leave the system?
 
• The drug takes effect in 10-15 mins after ingestion
 
• The effects last for 3-6 hours when taken without alcohol, and 36-72 hours when mixed with alcohol or other drugs
 
• In high dosages – unconsciousness or even a coma can occur within 5 minutes

Tool Mark Investigations

Tool marks

Tools are often used by criminals to force entry to premises and can leave behind evidence for the forensic scientist to find.

Two tools of the same kind and made by the same manufacturer may look the same, but through use each tool can acquire differences. It is these differences that make them unique.

Forensic Scientists are able to help the courts convict criminals by matching the marks on tools to those found at crime scenes.

Characteristics

The examination of tool marks, as with other physical evidence, is based on two characteristics – class characteristics and individual characteristics.

Class characteristics are those characteristics that are common to a group of objects. For example, a hammer has a distinctive shape and typical size.

Individual characteristics are those characteristics which are unique to a given object. They are generally as a result of wear and tear or may be caused by isolated incidents during manufacture. For example, you buy a new pair of shoes and as you wear the shoes, over time you will get scratches and gouges on the soles. These marks are unique to your shoes.

Tool Mark Impressions

Caused by the interaction of two objects, tool mark impressions are distinguished in a variety of ways:

Static marks are made when the tool is pressed into a softer material and leaves an impression. A good example is a crow bar being used to force open a window and a subsequent impression is left in the softer surface of the wood. The Forensic Scientist will examine the marks and may be able to identify what type and size of tool caused the damage.

Dynamic marks are made when a tool slides or scratches across a surface. Think of a key being dragged along the side of a car; such an instrument leaves behind a pattern of lines or striations in the metal of the car. The pattern of striations may be enough for the examiner to identify a match with the tool belonging to a suspect.

Cutting marks are a result of pressure being applied at both sides of an object and are often associated with scissors, wire cutters or shears. When used these tools can leave behind marks and striations along the cut edges of the material.

Multi-stroke marks are caused by repetitive action, such as a saw moving back and forth.

Examination

The Scene Examiner will examine and photograph the tool marks in situ. If appropriate, the Scene Examiner will remove the object with the marks and take it to the lab for further analysis. If this is not possible they will make a cast of the marks, generally using a silicone rubber.

A tool may be recovered that is suspected to have caused the damage and this will also be taken to the lab for further analysis.

The Forensic Scientist will make test marks using the suspect implement. The test mark and the mark recovered from the crime scene will then be compared.

The Forensic Scientist will examine and compare the striation patterns using the comparison microscope. By comparing and matching the striations the scientist can prove whether the tool is responsible for the impression.

Tools can also have trace evidence, such as paint flakes adhering, or in the case of a human victim, blood or other body fluids. This evidence greatly assists in the investigation of a crime.