Physical and chemical Physical and chemical evidenceevidence

BTEC First DiplomaBTEC First Diploma

Unit 10 : Forensic scienceUnit 10 : Forensic science

BTEC First DiplomaBTEC First Diploma

Unit 10 : Forensic scienceUnit 10 : Forensic science

Name: Pawel Name: Pawel

What is physical evidence?What is physical evidence?

Physical evidence includes:Physical evidence includes: marks and impressions such as marks and impressions such as

footprints and tool marks,footprints and tool marks, trace evidence such as fibres, glass trace evidence such as fibres, glass

and paintand paint

Physical analysis of blood can reveal Physical analysis of blood can reveal what took place while a crime was what took place while a crime was being committed.being committed.

Footprints Footprints

Shoe and boot prints are usually called Shoe and boot prints are usually called footprints, although a bare footprint footprints, although a bare footprint could have toe prints just like could have toe prints just like fingerprints. On hard surfaces, fingerprints. On hard surfaces, footprints of any kind can be footprints of any kind can be developed and lifted like fingerprints. developed and lifted like fingerprints. But impressions in soft material like But impressions in soft material like mud can provide greater detail of the mud can provide greater detail of the original shoe.original shoe.

Toolmarks Toolmarks

Even if a clever criminal has left no Even if a clever criminal has left no fingerprints, footprints or DNA, they fingerprints, footprints or DNA, they may have used a tool when carrying may have used a tool when carrying out their crime. It might be a jemmy out their crime. It might be a jemmy to force open a door or break a to force open a door or break a padlock, or even a weapon used to padlock, or even a weapon used to strike a victim or saw to cut up a strike a victim or saw to cut up a corpse.corpse.

Fibres Fibres

Fibres are easily shed or picked up. Fibres are easily shed or picked up. There are many different types. There are many different types.

They vary in cross-sectional shape.They vary in cross-sectional shape. Animal fibres such us wool are hairs Animal fibres such us wool are hairs

which therefore have characteristic which therefore have characteristic scales.scales.

Glass Glass

Window are often broken in burglaries. Car Window are often broken in burglaries. Car headlight are often broken in car headlight are often broken in car accidents. Spectacles, bottles and glasses accidents. Spectacles, bottles and glasses can be broken in a variety of can be broken in a variety of circumstances.circumstances.

They are thee different in types of glass:They are thee different in types of glass: colourcolour densitydensity refractive indexrefractive index

Blood splattersBlood splatters

Bloodstains can reveal an amazing Bloodstains can reveal an amazing amount of detail.amount of detail.

The pattern formed by a drop when it The pattern formed by a drop when it strikes a surface depends on size, strikes a surface depends on size, direction and force.direction and force.

For example:For example: blood dripping a short vertical blood dripping a short vertical

distance will form circles.distance will form circles.

What is chemical evidence?What is chemical evidence?

Chemical evidence (e.g. paint, drugs) Chemical evidence (e.g. paint, drugs) is a chemical which is left behind at is a chemical which is left behind at the crime scene which can be the crime scene which can be analysed by forensic scientists to analysed by forensic scientists to gain evidence.gain evidence.

There are different types of the There are different types of the chemical evidence like paper, gas or chemical evidence like paper, gas or ink. ink.

Chromatography Chromatography

This type of analysis can be used to This type of analysis can be used to identify many chemicals, including identify many chemicals, including dyes and drugs.dyes and drugs.

Gas chromatography and high Gas chromatography and high performance liquid chromatography performance liquid chromatography (HPLC) are in common use in forensic (HPLC) are in common use in forensic labs. Sample for analysis is placed in labs. Sample for analysis is placed in a vaporiser.a vaporiser.

Paint Paint

Paint fragments can be exchanged in Paint fragments can be exchanged in car accidents and when burglars use car accidents and when burglars use tools. Paint varies in colour tools. Paint varies in colour (pigments) an other chemical (pigments) an other chemical components, e.g. as in car paints and components, e.g. as in car paints and house paint.house paint.

Toxicology Toxicology

Forensic toxicologists are concerned Forensic toxicologists are concerned with substance that can caused harm with substance that can caused harm to the body. They identify substance to the body. They identify substance found at crime scenes or detect their found at crime scenes or detect their presence in the body.presence in the body.