A technique used to differentiate bullets that will be retrieved from the crime scene by crime scene officers.
Chemistry of ballistics in the crime scene Ellie Cox
What are they?...• Ballistics is the science that deals with the motion and the effects of projectiles such as bullets and also rockets.• Ballistic body- The gun will be referred to this at a crime scene.• Ballistic science will analyse the projectiles (bullets) that are released from the ballistic body, the gun.
Internal ballistics…• Look at things such as the passage of a bullet through the barrel of the rifle, to see any damage of the passage from the projectile.Transition ballistics…• Analysing the bullet or projectile when it leaves the barrel and the pressure behind it.
External ballistics…• Looking at the space or air that the projectile passes until it gets to its desired target e.g. flesh/material.Terminal ballistics…Analysing the interaction of the bullet with its target e.g.flesh/material.
Firearm ballistics• This type of ballistics are used within a crime scene to analyse the tool mark evidence allowing them to match guns or any other tools to certain bullets and crimes.
Bullet comparisons…Within crime scenes visual analysis is used to compare bulletsretrieved from the crime scene and link them with a suspects bullet.To do this a bullet will be fired from the suspects gun into a watertank, doing this they will be able to link certain bullets to certainsuspects.They can use the lands, grooves and twists on the bullets to tell them:• The manufacturer,• The model• The model• And sometimes the year of the make.
Ballistics analysis…• Bullet casing• Evidence will be retrieved in a evidence bag and necessary forms will be filled out before any evidence is used and experimented on.
• Once this has been done, scientists are able to use a comparison microscope that will have two separate lenses allowing them to differentiate two different bullets using clues like serial numbers.•• The comparison microscopes are also used in crime scenes to differentiate suspects finger prints.
Pressed marking analysis…• Pressed marking analysis is a vital technique within crime scene science, using chemistry to initiate serial numbers from bullets that have been filed off by the offender. Serial numbers on bullets will allow us to link the bullet with certain guns, therefore linking them with criminals with the same gun and also the same bullets that can be linked to other crimes.
• Chemistry has allowed us to be able to retrieve the serial number if it has been filed off…• First off all the area of the bullet will be smoothed down using sand paper,• Secondly it will be rinsed with acetone, which is an organic compound used as the main ingredient within nail varnish remover,• Next copper on a cotton bud will be introduced and rubbed on the area, this will then produce a chemical reaction between the iron• This chemical reaction will then cause the serial number to reappear on the area.
References…Bill Maher. (Aug 30th 2010). FIREARMS IDENTIFICATION AND BALLISTICS.Available: http://www.drtomoconnor.com/3210/3210lect05a.htm. Last accessed26th Jan 2011.Lisa Steele. (2009). Ballistics. Available:http://www.aware.org/arttruelaw/5450051chap1_abs.pdf. Last accessed 25thJan 2011R.Conan-Davies. (2006). Crime scene investigation chemistry. Available:http://clearlyexplained.com/answers/CSIchemistry.html. Last accessed 26th Jan2011http://www.forensicsciencescholars.org/resources/video/forensic-chemistry-lab-ballistics - Video of pressed marking analysishttp://www.google.co.uk/imgres?q=bullets+serial+numbers&um=1&hl=en&tbm=isch&tbnid=sLh2iokR9dS79M:&imgrefurl=http://www.ssaa.org.au/stories/handguns-the-versatile-357-magnum.html&docid=gYL5Drrl5nUlHM&imgurl=http:// -Image of bullets