32.3 Using Physical Techniques to analyse evidence

1. 32.3 Using Physical Techniques to analyse evidence

2. Ballistics • Ballistics is the study projectiles motion. • Internal ballistics - the study of projectiles in the weapon • External ballistics - the behaviour of the projectile through air • Terminal ballistics - the study of the penetration different mediums by projectiles

3. Terminology

4. Types of Firearm PISTOL REVOLVER • Handguns • Small, light, compact, concealable, less powerful • Used for short-range firing (eg self-defence) • Revolver – cheap, simple, reliable, 6 shot limit, slow reload • Pistol – uses magazines, self-loading, 10 shot limit

5. Types of Firearm • 2. Rifles • Longer barrel than hand guns • Large so hard to carry and conceal • More accurate and more powerful

6. Types of Firearm • 3. Shotguns • Used for hunting game in flight or on the ground • Single- or double-barrelled • Single shot, pump action, semi-automatic

7. Rifle and handgun cartridge • The ammunition comes in many sizes. • Closed metal cylinder carrying firing cap & a powder. • When striking the cup, the powder burns rapidly producing huge volume of gas that propels the bullet.

8. Shotgun cartridges • Fire a large number of small spherical lead or steel shot (slugs, buckshot or birdshot). • Ammunition consists of cartridge (metal base containing a central firing cap supporting plastic or cardboard tube). • Inside the cartridge is a wad of paper & cardboard, with a mass of lead pellets.

9. Rifling • Inside the barrel of handguns and rifles (not shotguns) is a number of spiral grooves (bore). • This makes the bullet spin as it leaves the barrel, giving it greater stability. • Every bullet fired will have groove marks on it.

10. Calibre • The internal diameter of the barrel in handguns and rifles • Shotguns have gauges – the number of lead balls of bore diameter needed to equal 1lb. • In UK, calibre is in mm eg 7.62mm Winchester • In the US, imperial measurements are used eg .30 Winchester (30 hundredths of an inch)

11. Other ballistics evidence… Discharge Residue – Every time a gun is fired, a residue is discharged. Chemical tests can be carried to determine the presence and nature of these residues. Ballistic Fingerprints - As a gun is used, it develops irregularities in the bore that can scratch the surface of the bullet as it leaves. Microstamping - Some guns imprint a stamp onto each cartridge case ejected which can be used to match the cartridge to a specific gun.

12. Trajectory Can be used to reconstruct a crime to find out where the shooter was in relation to the victim.

13. Wound Patterns • Entrance wounds have an ‘abrasion collar’ where the projectile has “dragged” the skin into the wound. • “Pink/red” staining of the skin (due to carbon monoxide laden gases producing carboxyhaemoglobin) • Gunpowder blackening of the wound edges & surrounding skin (from soot & unburned propellant gases). • Circular bruise over the skin due to muzzle impact.

14. Range • Near Discharge(a few cm) • Small, dry, reddish strippling caused by unburned powder & small metal fragments striking the skin • Smoke soiling • Lack of muzzle mark • Intermediate Discharge (20cm - 1m) • Less smoke soiling but powder “tattooing” still present • Burning will be present • The rim of the wound is irregular forming what is called ‘rat-hole’.

15. Range • Long Range(2m - 3m) • Satellite pellet holes will be seen around the central wound, which diminishes in size as the range increases. • the spread of shot (cm) = 2.5 times the range (m). If the wound pattern is 20 cm across the discharge was 7 – 10 m so couldn’t be a suicide. • Very Long Range (20m – 30m) • Abrasion collar • No smoke soiling, burning or powder tattooing.

16. Wounds: shotgun vs rifles

17. Exit wound

18. Exit wound

19. Handwriting AnalysisHandwriting AnalysisHandwriting AnalysisHandwriting AnalysisHandwriting AnalysisHandwriting AnalysisHandwriting AnalysisHandwriting Analysis

20. So what is hand-writing analysis? • It is NOT graphology - a controversial pseudoscience that analyses handwriting in terms of psychology. • It is: “The examination of handwriting to assess potential authorship via comparison of samples of handwritten material”.

21. Traits • Letter form - curves, slants, the proportional size of letters, the slope of writing and the use connecting links between letters. A person may form a letter differently depending on where the letter falls in a word. An analyst will need examples of each letter in each placement. • Line form - how smooth and dark the lines are which indicates how much pressure the writer applies and the speed of the writing. • Formatting - This includes the spacing between letters, the spacing between words, the placement of words on a line and the margins a writer leaves.

22. Exemplars • ­Analysing handwriting requires many comparison samples (exemplars) - documents that have a known author. • During the Lindbergh kidnapping in 1932, the kidnapper sent 14 notes to Lindbergh with ransom demands. • Handwriting analysts easily determined that all of the notes were written by the same person. • Exemplars from the main suspect, Richard Bruno Hauptmann, were obtained for comparison.

23. Exemplar Tables • Compile a table that catalogues each varied form of every letter that appears, taking into consideration all traits. • In forensics, they would "copy" each letter form using a digital camera and would make separate tables for uppercase and lowercase letters.

24. 1956 Weinberger Kidnapping The FBI matched the top two phrases “your baby sitter” taken from the ransom note to the bottom two written by the prime suspects whilst in custody.

25. Forgeries

26. Activity 32.3B • Get two people in the class to write: “The quick brown fox jumped over the lazy dog.” • Compare the traits of the different handwriting and identify the differences. • Now ask the individuals to try to forge each others’ handwriting. Again compare the traits.