SALIVA AS A PREDICTOR OF AGE

Promising research now shows that DNA Methylation of human saliva can be utilized to predict a person's age with a modest degree of accuracy. No doubt the technique will improve with refinement and ongoing technological advances. Inferential methods like this are invaluable, because they allow forensic investigators to build a suspect's profile without having to rely on database matches (as is the case with fingerprints, DNA, etc.).

Read a summary of the research here:

http://www.popsci.com/science/article/2011-06/saliva-science-new-forensics-tool-can-determine-age-suspects-spit

Then check out the genuine research publication on PLoS ONE:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0014821

ABSTRACT:

From the moment of conception, we begin to age. A decay of cellular structures, gene regulation, and DNA sequence ages cells and organisms. DNA methylation patterns change with increasing age and contribute to age related disease. Here we identify 88 sites in or near 80 genes for which the degree of cytosine methylation is significantly correlated with age in saliva of 34 male identical twin pairs between 21 and 55 years of age. Furthermore, we validated sites in the promoters of three genes and replicated our results in a general population sample of 31 males and 29 females between 18 and 70 years of age. The methylation of three sites—in the promoters of the EDARADD, TOM1L1, and NPTX2 genes—is linear with age over a range of five decades. Using just two cytosines from these loci, we built a regression model that explained 73% of the variance in age, and is able to predict the age of an individual with an average accuracy of 5.2 years. In forensic science, such a model could estimate the age of a person, based on a biological sample alone. Furthermore, a measurement of relevant sites in the genome could be a tool in routine medical screening to predict the risk of age-related diseases and to tailor interventions based on the epigenetic bio-age instead of the chronological age.

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FINGERPRINTING UNDER SCRUTINY

Here are a few articles commenting on fingerprint analysis, its usefulness and reliability, as well as our common perceptions regarding the practice:

Fact Is, Science Has Never Put Its Finger On Prints

The Myth of Fingerprints

ACE-V - Is It Scientifically Reliable and Accurate?

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EVIDENCE OF BLUNT FORCE IMPACT ON FABRICS

I've been reading some fascinating and extremely well-written journal articles regarding the forensic evidence of violent crime left on clothing. The following is excerpted from Daroux, et al. [1]

ABSTRACT:
Blunt force assault is a growing issue worldwide. In New Zealand, recorded cases of grievous blunt force assault increased steadily from 1011 in 1999 to 2139 in 2008 [2]. In many cases of blunt force assault victims are struck on parts of their body covered by clothing, yet the use of damage to apparel as forensic evidence largely appears to have been overlooked. The current research investigated blunt force impact
(BFI) damage in common apparel fabrics and the effects prior and post-laundering had on this damage. Two 100% cotton fabrics (single jersey knit, bull drill) were impacted as single and double layers using an impactor representative of a hammer face, the force transmitted through specimens was measured and impulse calculated. Impacting and laundering were completed cumulatively to establish the effects of impact damage on new, dimensionally stable (laundered 6 times) and aged fabrics (laundered up to 30 times), and the effects of laundering on impacted specimens. BFI left recognisable patterns of damage in specimens, although the extent of this damage varied. Laundering after the impact event altered the visible and microscopic damage. Laundering previously impacted fabrics produced holes in some specimens and some fibres exhibited failure characteristic of blunt force impact.

Fig. 5. Typical examples of fibre failure: (a) impacted, not laundered; b–d impacted then laundered fibres (b = example of fibre retaining flattened appearance, little fibrillar separation after laundering, c and d = fibres regained more three-dimensional appearance; c = short, uneven break, perpendicular to fibre axis, d = examples of messy, bulbous and collapsed fibre ends after laundering).

5. Conclusions
BFI can cause recognisable damage in apparel fabrics. Laundering apparel fabrics prior to impacting did not significantly alter the visible damage. Laundering apparel fabrics after impacting did not generally destroy evidence of BFI damage, but rather altered the damage. BFI damage to fabrics varied considerably due to other variables investigated, i.e. fabric structure, number of layers. Further research is required to develop comprehensive knowledge regarding BFI damage in apparel fabrics. Of particular importance would be consideration of incorporating an underlying human
tissue simulant, as fabric damage due to BFI is likely to be significantly affected by the underlying substrate. Different methods can be used to compare BFI damage. The most effective method investigated in this work, but one which needs to be
interpreted with care was SEM.

SOURCES:

1. Daroux, F.Y., Carr, D.J., Kieser, J., Niven, B.E., Taylor, M.C. (2010). Effect of laundering on blunt force impact damage in fabrics. Forensic Science International Vol. 197 (21-29).

2. Statistics New Zealand, New Zealand recorded crime tables, available online at
http://www.stats.govt.nz (14.02.08). [This is a direct reference from the journal article.]

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HAND BACTERIA FOR INDIVIDUALIZATION

One of the most interesting and recent developments in individualization techniques is detailed in the Homeland Security Bulletin below:

New Biometric Identifier

Each individual has "personal" bacteria communities living on the fingers and palms of individual computer users; members of these communities are deposited on keyboards, mice and other things we touch; the link between the bacterial communities and the bacterial DNA signatures of individuals may soon become a tool in forensic identification.

I'll be posting more on this subject as the methodology and science develop.

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