BPA
Definition
Bloodstain Pattern Analysis. Reconstruction of events from spatter geometry. Sits outside this syllabus bullet but commonly tested in short-answer form alongside detection.
- Stands for
- Bloodstain Pattern Analysis
- Input
- Spatter geometry, shape, distribution, density
- Output
- Reconstruction of events at a scene
- Related process
- Blood stain detection and identification
Common questions
How does BPA relate to blood detection tests at a scene?+
Detection tests such as presumptive colour or luminol tests establish that a stain is likely blood in the first place. BPA is the separate, later step of interpreting the confirmed stains' shapes and distribution to infer what happened, such as the direction or type of force involved.
What can BPA not tell an investigator on its own?+
Pattern shape can suggest a mechanism, such as impact or projection, but it cannot by itself identify a specific weapon, confirm whose blood it is, or fix an exact time; those require separate DNA analysis, weapon examination and other scene evidence.
Related terms
- Benzidine Test
- Historical presumptive test using benzidine and hydrogen peroxide to give a blue colour. Banned for routine use because benzidine is a confirmed...
- Confirmatory Test
- A test with sufficient specificity to establish the identity of a biological fluid for reporting purposes. Examples include Takayama and Teichmann crystal...
- Kastle-Meyer Test
- Phenolphthalein based presumptive test. Reduced phenolphthalin is oxidised by haem peroxidase activity in the presence of hydrogen peroxide to give a pink...
- Leucomalachite Green (LMG)
- The reduced, colourless form of malachite green. It is oxidised to the coloured malachite green form by active oxygen released when haemoglobin...
- Luminol
- A chemiluminescent reagent (5-amino-2,3-dihydro-1,4-phthalazinedione) that produces blue-white light on contact with haemoglobin-derived iron. Detects blood diluted to 1:10,000,000 or more. Used as...
- Presumptive Test
- A fast, low-cost, class-specific screen used to triage a caseload before instrumental work begins. Examples are Marquis reagent for opioids and amphetamines,...
- Takayama Test
- Confirmatory crystal test. Pyridine, glucose and sodium hydroxide convert haem to pink, feathery pyridine ferroprotoporphyrin (haemochromogen) crystals.
- Teichmann Test
- Confirmatory crystal test. Glacial acetic acid and sodium chloride convert haem to brown, rhombic haemin (ferriprotoporphyrin chloride) crystals. Older, less reliable on...