development of bloody fingerprints

Question 1

two types

Answer 1

• those that use the heme grouping

- those that react with proteins on their breakdown produce

Question 2

techniques using heme grouping

Answer 2

1863- schonbein used hydrogen peroxide

1804 Adler and Adler used benzidine

1906 kastle Meyer test uses phenopthalein

• subject to false negatives e.g with bleach
• rely on peroxidase activity of heme group
• coupled to the oxidation of colourless reduced dyes

Question 3

luminol

Answer 3

1853 – first synthesized
1928 – chemiluminescence of luminol first reported
1937 – Specht was first to use luminol to detect blood at a crime scene
1951 – Grodsky formulation for luminol reported
2001 – Bluestar introduced as an improved luminol reagent
-is extremely sensitive and long lasting
-applied numerous times and still receive DNA typing results.
-however more time consuming to prepare

• can damage fine detail of blood contaminated fingerprints
• false positives in the presence of chemical oxidants and catalysts
• negative results with a catalytic test proves the absence of blood

Question 4

benzidine

Answer 4

enzyme in blood oxidises benzidine to a blue coloured derivative
- banned in 2974 as carcinogenic

Question 5

phenolphthalein

Answer 5

alcohol used to dissolve as its insoluble in water

• non destructive to sample
• if sample contains haemoglobin it will go pink

Question 6

fluorescein

Answer 6

• Synthesised by von Baeyer in 1871
• 1910 First use for detection of blood was by Fleig in urine
• 1995 first use in a forensic setting to determine blood by Cheeseman

Before use fluorescein is reduced to colourless fluorescin by zinc.
Fluorescin and H2O2 are added to bloody print
Heme catalyses reaction of H2O2 oxidation of Fluorescin to fluorescein

fine bloodstains and blood smears will fluoresce when treated with fluorescein

Question 7

tests for proteins and breakdown products

Answer 7

Later tests used compounds that bound to the proteins in blood to visualise prints e.g amido black as well as other acid dyes, gentian violet,

ninhydrin and DFO etc. targets amino acids in blood by a different mechanism

Sensitive technique
proteins water soluble have to be denatured and fixed before staining

Question 8

staining proteins in blood

Answer 8

Fixing solution- ppts proteins
Staining solution- prevents blood diffusing away
Washing solution

• most effective protein dyes are acid dyes

Question 9

amido black (acid black 1)

Answer 9

1962 – amido black used to stain proteins
1970 – methanol-based AB solution reported in UK
1989 – Hussain et al. report a water-based AB reagent
2004 – UK Home Office Scientific Development Branch report on a WEA formulation

can be absorbed by porous surfaces so need to test surface first

Question 10

acid yellow 7

Answer 10

• Stains proteins to give pale yellow colour
• Fluoresces bright yellow under blue-green light
• Not recommended for porous surfaces

Question 11

critical issues

Answer 11

Correct sequence of processing must be used

Other tests should be done to confirm whether mark really is in blood

Fixing stage is crucial otherwise ridge detail may diffuse out

Current solutions are inflammable and have a low flash point of 30oC