Crime Scene Management: Chapter 5.1, 5.8, 5.9 - for practical

5.1 introduction

can be used to establish presence at scene and actions taken

chemical/powder enhancement and treatment

photograph

ridge friction skin formation

implications of treatments on latent fingerprints

wide range of optical, physical, digital and chemical techniques are available for the detection and enhancement of latent finger marks

best results are obtained if a methodical and logical sequence of techniques is applied

application of many different techniques or reagents will often increase the number of finger marks detected and/or improve quality of those detected

choice of best sequence of techniques depend on several factors that include:

nature of surface and presence of any particular contaminants
what the evidence originates from
environmental factors
the likely age of any evidential finger marks

emphasis should always be placed on optical techniques as these are non-destructive

results obtained from optical methods will be better than those obtained by physical or chemical methods

chosen techniques should be applied with caution

prolonged use of UV light could degrade or destroy DNA

5.8 identification of common locations for prints

each of the following factors independently or in combination can account for the lack of prints on any given surface:

individuals don’t always have a sufficient quantity of perspiration and/or contaminants on their hands to be deposited
when someone touches something, they may handle it in a manner which causes the prints to smear
the surface may not be suitable for retaining the minute traces of moisture in a form representative of the ridge detail
the environment may cause the latent print to deteriorate
the perpetrator may be wearing gloves

CSI establish the points of entry and egress

development of latent prints with powder should be left to end of examination

CSI should talk to occupier and assess out of place items

consider what is suitable for treatment at scene and what needs to be recovered

if items are recovered, ensure appropriate packaging to avoid damage

protect any potential latent finger marks

continuity

where possible recover elimination prints from injured party and those with legitimate access

reduces disclosure of unidentified material

remember with appropriate treatment whether it is powder or chemical, many surfaces can and should be considered for treatment to enhance latent finger marks

understanding sweat composition in latent prints

techniques such as MALDI MS imaging used to investigate chemical profiling of latent marks - identify fingerprint activity of suspect prior to crime being committed

5.9 use of powdering techniques to enhance latent finger marks

powders can be magnetic and fluorescent meaning they can be applied to an increasing range of surfaces that may yield enhanced latent finger marks

effectiveness depends on chemical and physical makeup of powder and experience and skill of operative and applicator

powders made of flakes - far more sensitive, that produce consistently good results on most applicable surfaces

lifted and placed onto plastic sheets for recovery to a central lab

less sensitive powders can be used at scenes

black and white powders used readily effectiveness depending on skill and expertise of photographers to get best enhancement

powders used on any surfaces smooth and clean

easy to deploy and use

extremely effective on glass

unusable if wet or dirty or rough or contaminated

powders require adequate illumination to highlight enhanced material

mindful of destructive properties of powders may inhibit further treatments or processes

poor technique will result in finger marks that are possibly of insufficient quality for examiners to evaluate

5.9.1 brushes and magnetic applicators

variety of applicators e.g. glass fibre, carbon fibre, animal hair varieties

when applying aluminium powder - glass fibre brush considered best choice

powdering of window isn’t to be considered in same way as painting onto a wall

if powder applied too heavily - mark is flooded and no detail shown

build up application

can do sweeping motion with brush or twizzle method

how to charge brush

loading brush with powder ready for application

shake out brush away from area so excess powder can be removed to prevent any possibility of over-powering

learned with experience and amount of powder required for optimum results

once mark is developed using either method its necessary to clear mark using unsoiled animal fur brush