This 2018 Austrian review subject was forensic applications of epigenetic clock methodologies:
“The methylation-sensitive analysis of carefully selected DNA markers (CpG sites) has brought the most promising results by providing prediction accuracies of ±3–4 years, which can be comparable to, or even surpass those from, eyewitness reports. This mini-review puts recent developments in age estimation via (epi)genetic methods in the context of the requirements and goals of forensic genetics and highlights paths to follow in the future of forensic genomics.”
The point of forensic analysis techniques should be to find the truth about an individual. Doesn’t the principle of “All presumptive evidence of felony should be admitted cautiously; for the law holds it better that ten guilty persons escape, than that one innocent party suffer” still hold?
The methods’ limitations weren’t discussed. Here are some concepts not mentioned in the review:
1) Summary statistics that describe a group or population NEVER necessarily describe an individual member.
For an epigenetic clock methodology example, take a look at Figure 2A in Using an epigenetic clock to assess liver disease. 16 of the 18 individual age acceleration estimates of the control group subjects aren’t close to the median value!
2) The reviewer outlined basic DNA methylation analysis:
“The most commonly pursued approach for analysing CpG sites is sequence analysis of bisulfite-converted DNA, during which single-stranded genomic DNA is treated with sodium bisulfite that deaminates unmethylated cytosine to uracil, while methylated cytosine remains unaffected.
With increasing age, not only genome-wide DNA hypomethylation has been observed but also regional DNA hypermethylation of CpG islands.”
The basic limitation of this analysis wasn’t mentioned, but A study of DNA methylation and age said:
“Due to the methods applied in the present study, not all the effects of DNA methylation on gene expression could be detected; this limitation is also true for previously reported results.
The textbook case of DNA methylation regulating gene expression (the methylation of a promoter and silencing of a gene) remains undetected in many cases because in an array analysis, an unexpressed gene shows no signal that can be distinguished from background and is therefore typically omitted from the analysis.”
3) Another omission was that the numbers and types of targets in the discussed DNA methylation technique were severely limited per The primary causes of individual differences in DNA methylation are environmental factors:
“A main limitation with studies using the Illumina 450 K array is that the platform only covers ~1.5 % of overall genomic CpGs, which are biased towards promoters and strongly underrepresented in distal regulatory elements, i.e., enhancers.
The reviewer didn’t provide convincing justifications for using gene expression profiling to obtain convictions. Was it too much to expect a mini-review to offer a balanced view of using epigenetic age estimation in forensic analyses?
https://www.karger.com/Article/FullText/486239 “Age Estimation with DNA: From Forensic DNA Fingerprinting to Forensic (Epi)Genomics: A Mini-Review”