Forensic Biology

What are the three processes that reveal latent fingerprints?

1. Ninhydrin spray = reacts with amino acids from sweat and creates a purple product

2. Iodine fuming = another solution that reacts with other components of sweat

3. Dusting = aluminium powder brushed over the prints, the dust sticks to sweat and leaves a print

What is the process for analysing DNA?

Extract = the DNA

Amplify = bits of the DNA with a PCR machine where they are replicated into pairs to analyse

Analyse = the DNA fragments using Gel Electrophoresis (where DNA is negatively charged therefore moves towards the positive charge)

Compare = the DNA pattern by looking at the Gel Electrophoresis spread ad comparing to DNA libraries

What is DNA?

• often found in blood stains, hair, fingerprints, semen, saliva

• these all contain cells where there is a nucleus (mitochondria) this is where the DNA is found

• DNA identification uses non-coding DNA meaning it is more likely to be unique

• it utilises Short Tandem Repeats (STRs)

What are Diatoms?

• single-celled algae that live in water and soil

• extremely robust and durable

• fresh water diatoms = they drowned in fresh water

• a botanist can determine if it is a fresh or marine water diatom

• help identify where someone has drowned in a case/investigation

What are fingerprints?

• latent fingerprints cant be visibly seen but are still present in an environment

• left by sweat that form on the ridges of a fingerprint

• three types:

  • loop

  • whorl

  • arch

• fingerprint recognition and comparison can be done digitally

Estimating time since death with insects

• insects can be of use in identifying time of death by observing life cycles

• there are 6 stages over 345 hours (2 weeks)

• later after death the body is found the less precise this method gets - it is a rough science

• example: blowfly = lays eggs soon after death, approx. 22 + 27 + 23 = 72 hours since death