Chapter 28

Forensic Investigation

Although in principle all individuals belonging to the same species share the same

DNA, the vagaries of sexual recombination (Sect. 14.7.3) ensure considerable vari-

ability in the non-coding parts of the genome. Even identical twins show some

differences. ¹ An individual’s genome sequence is thus a unique attribute of the indi-

vidual, much as the various phenotypic attributes traditionally used for verifying

identity, such as the face, fingerprints, iris pattern, signature etc. Unlike the phe-

notypic attributes, which are analogue in nature and show a continuous spectrum

of variability, the DNA sequence is digital in nature and an exact description is in

principle possible.

The genome is, however, too large and complex for it to be practically useful for

establishing identity; even the latest sequencing technologies still require at least sev-

eral hours to sequence an entire (human) genome (Sect. 17.1.5), whereas mensuration

of a fingerprint requires a fraction of a second, and automatic face recognition and

matching with passport data nowadays only takes a few seconds thanks to efficient

pattern recognition algorithms (Sect. 13.1).

One solution to the impediments of lengthy time (and cost) of whole-genome

sequencing would be to sequence shorter lengths of DNA. The appropriate length

is determined by the uncertainty (“noise”) in the sequencing procedure; ² the length

should be sufficient to reduce the equivocation to level deemed to be appropriate in

a given context (for example, in a court of law—it is a matter of convincing a judge

or jury or both and there is no absolute criterion). This, however, then poses the new

problem of how to select those lengths in such a way that the selection is the same

for samples being compared.

Forensic medicine (in German, Rechtsmedizin) is an important branch of the med-

ical application of genetic analysis. Its efficacy is due to the extraordinary fugacity

1 This is without consideration of epigenetic differences manifest, for example, in the pattern of

DNA methylation. This, however, usually evolves during the lifetime of an individual.

2 See Sect. 7.5.

© Springer Nature Switzerland AG 2023

J. Ramsden, Bioinformatics, Computational Biology,

https://doi.org/10.1007/978-3-030-45607-8_28

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