Lecture 13: Ballistics Flashcards
Definitions
> Ballistics - the scientific study of a projectile in flight
Forensic ballistics - the application of science to law in identifying used cartridge cases & fired bullets & connecting them to a particular firearm
Interior ballistics
the study of projectiles in weapons
External ballistics
the study of projectiles in the air
Terminal ballistics
the study of projectile penetration of solids
Wound ballistics
the study of projectile penetration of tissues
Kinetic energy
> A moving projectile has kinetic energy proportional to its weight & velocity
The wounding effect of a projectile is produced by transfer of kinetic energy from the projectile to the tissues
The greater the kinetic energy of projectile, the greater the wounding potential – hence the great wounding potential of high velocity projectiles
If a projectile does not exit the body, then all its kinetic energy has been transferred to the tissues
If the projectile exits the body, then only some of its kinetic energy has been transferred to the tissues
Firearm
> The legal definition of a firearm according to the UK Firearms Act, section 57, 1968 is………. ‘a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged’
The firearm is the means of aiming & discharging the projectile & imparting stability to it
The role of a firearm
> Discharge a projectile with sufficient energy to kill
Ensure the projectile travels in the required direction
Ensure that a bullet, as distinct from shotgun pellets, arrives at its target nose first
Small arms
> Includes explosive-operated small arms of every description, whether of present use or future invention, adapted for the discharge of shot, bullet or other projectile.
Such arms include:
– shotguns
– rifles
– pistols
– revolvers
– cattle killers
– line throwers
– signal pistols
– alarm guns
– nail driving or other industrial tools
Fire arms legislation
> Prohibited weapons:
– whether it is such a lethal weapon as aforesaid or not,
– and any component part of such a weapon,
– and any accessory to such weapon designed or adapted to diminish the noise or flash caused by the firing of the weapon
Proof of shot guns and small arms
> Proof – is the compulsory and statutory testing of every new shotgun or other small arm before sale, to ensure so far as is practicable, its safety in the hands of the user
Reproof – is the similar testing of a small arm which has previously been proved.
The Proof Acts lay down that no small arm may be sold, exchanged or exported, exposed or kept for sale or exchange or pawned unless and until it has been fully proved and duly marked
The maximum penalty is £1,000 for each offence, but with provision for higher penalties where, for instance, the sale of a number of guns constitutes one offence
Alteration to or the forging of proof marks is a serious offence.
Ammunition: cartridges and bullets
> Ammunition – what is, or may be, fired from a gun (including an air weapon)
Comprises the cartridge case, primer, propellant & bullet in its entirety
Bullet – the part of the ammunition that is projected from the firearm
Cartridge – metal or plastic casing which contains the primer & propellant, & forms a gas-tight seal with the bullet
Propellant – a compound, such as nitrocellulose, which will burn explosively to produce a large volume of gas within the cartridge
Rim – extraction feature & Headstamp – details of calibre & manufacturer
Primer – mixture of compounds that explode when compressed, igniting the propellant
Forensic ballistics: analysis of firearms
> Firearm analysis is a specialist discipline involving:
– Evidence recovery at the crime scene
– Trace evidence recovery from clothing, hands, wounds etc.
– Ballistics (i.e. study of how the bullet behaved in flight)
Fire arm identification
‘any discipline of forensic science which has its primary concern to determine if a; –Bullet/Cartridge case or /Other ammunition component was discharged (fired) by a particular firearm’
Analysis of firearms
> Potential applications:
– Identifying who fired a weapon, for e.g. determining whether a particular individual was responsible for causing an injury to another party
– Matching weapons & comparing used bullets, for e.g. when linking a weapon to a particular crime scene
– Providing evidence in the reconstruction of events, for e.g. establishing likely distance from which a weapon was fired, to corroborate the version of events of a suspect or witness
Forensic evidence on a semi-automatic pistol
> Firing pin mark
Breech marks
Rifling marks
Ejector marks
GSR
Gun oil traces
Metallic residues
Fingerprints
DNA
Role of forensic scientist
> Will focus on a particular aspect including:
Ballistics – examine what happens to the bullet inside the barrel of a firearm during flight and when it reaches its target
Analysis of Gunshot Residue (GSR) – examine hands &/or clothing for primer residue from a person who has fired a weapon
Physical fits & microscopic comparisons – examine any marks that may have transferred to a bullet as it is fired from a weapon
Determination of the serial number of the firearm – examine an obliterated serial number using chemical treatment
Headstamps
– Virtually all cartridge cases have head stamps on their bases
– Head stamp is a series of:
>Letters
>Numbers
>Symbols
>&/or trade names
Rifled weapons
> The weapon can be centrefire or rimfire weapon (based on location of primer)
Centrefire & rimfire refers to the location the firing pin will strike the primer on the cartridge to detonate the primer
Handguns
> Pistol (semi-automatic)
Revolvers:
Single action (hammer has to be pulled back & cocked, manually, before firing)
Double action (pulling of the trigger causes the hammer to cock & fire)
Shoulder arms or long guns
> E.g. Rifle
A rifle is a long gun with a rifled barrel, usually described by the way in which the weapon is loaded
They act much like handguns except the bullets fired from a rifle travel much further & with greater velocity
Examples of rifled long guns include:
– Semi-automatic action
– Pump or slide action
– Lever action
– Bolt action
– Single shot action
Rifle ammunition
> Rifle ammunition can be military (doesn’t break apart in the body) or hunting (fragments)
Ammunition includes:
– Lead bullets
– Semi-jacketed bullets
– Full metal jacketed bullets
Smooth bore weapons
> E.g. Shotguns
Classified the same way as rifles – by way in which they are loaded
Semi-automatic , pump or slide action, lever action, bolt action, single shot action:
– Top break action,
– Double action (side by side or over & under)
Shotguns may have a tapering of the barrel end called a choke.
Choke condenses the shot as it comes out of the barrel, allowing for a tighter pattern of shot to travel of a longer distance
Shot gun ammunition
> Ammunition for shotguns:
– Birdshot
– Buckshot
– Slugs
Shotgun shells ammunition are encased in plastic or paper containers which travels for a distance with the shot.
Locating these can help determine the muzzle from target distance:
– Heavy plastic cup & plastic wadding may be found up at a distance of up to 6m
– Paper & filler wads may be found in distance up to 5m
– Polyethylene filler granules can be found at distances of 3-3m
– Ball powder up to 1m
