EDITORIAL
Forensic genetics
Like other subjects, forensic genetics gradually
emerged and developed through long-term social
practice. Following the discovery of the ABO blood
groups by Landsteiner in 1900 [1], human blood
type was used in identification, and forensic genetics
entered the scientific age. In 1910, the French crim-
inologist Edmond Locard proposed the Locard’s
exchange principle [2] and stated that “every contact
leaves a trace,”which laid the foundation for modern
forensic science. In 1926, Thomas Hunt Morgan [3]
proposed a theory of genes, which provided the basis
for the development of forensic genetics. In 1953, the
discovery of the double-helical structure of DNA
enabled the start of forensic genetics research at the
molecular level [3].
One of the central aspects of forensic genetics is
the use of genetic markers, which are the easily
identifiable phenotypes of genotypes. Genetic
markers generally have features such as strong poly-
morphisms, codominant expression and ease of
observation and recording. With the development of
genetics, the use of genetic markers has also devel-
oped steadily. To date, the development of genetic
markers has gone through four major stages charac-
terized by the use of morphological markers, cyto-
logical markers, biochemical markers and molecular
markers. In particular, this present special issue pro-
vides an introduction to the application and devel-
opment for molecular markers in forensic areas.
During the early 1990s, short tandem repeats
(STRs) were used for the first time as key molecular
markers in human paternity testing. The first foren-
sic multiplex amplification STR kit was developed
by Britain’s Forensic Science Service (FSS) and
included four genetic loci: TH01, vWA, FES/FPS
and F13A1. Today, commercial STR kits can gener-
ally detect 15–20 STR loci at one time. With the
advancement of fluorescent marker techniques, six-
color fluorescent marker STR kits have appeared on
the market, and 25–30 STR loci can be detected.
The International Society for Forensic Genetics
(ISFG) has drafted a guide to the forensic validation
of STR kits, and this guide provides excellent stand-
ards and guidance for the forensic application of
STR kits.
The rapid development of massively parallel
sequencing (MPS) has attracted widespread atten-
tion among forensic genetics researchers. STR typ-
ing based on capillary electrophoresis can only
reflect differences in length; however, MPS can also
reveal differences in the internal sequence and flank-
ing structure of STRs, which tremendously increases
the available genetic information and provides a
new possible method for difficult cases involving
complex kinship identification and the resolution of
mixtures. In addition, the development of MPS has
also promoted metagenomics research. In recent
years, metagenomics has developed as a new branch
of microbial ecology that addresses the microbial
composition and diversity of different environments,
and microbial community members’relationships
with each other and their environment.
Metagenomics is gradually being applied in areas
connected with forensic identification such as indi-
vidual identification, identification of the source of
biological stains in crime scenes and the detection
of drug abuse, which has also brought new research
opportunities.
Since forensic polymorphic STR loci are limited
in number and cannot provide more functional
information, which hampers the effectiveness of the
application in forensic community, a new type of
genetic marker, single nucleotide polymorphisms
(SNPs), may replace STRs in the future, although
this process may take a considerable period of time.
Compared with STR loci, SNP sites have a lower
mutation rate, approximately 10
8
[4], and the amp-
lification products of individual SNP sites can be
very short, which makes SNPs suitable for the ana-
lysis of highly degraded forensic samples. SNP ana-
lysis already plays an important role in the
identification of individuals after mass disasters.
Furthermore, SNPs are linked with multiple pheno-
types, such as individual’s skin color, sclera color,
hair curliness, information concerning ethnic origin,
differences in alcohol metabolism and susceptibility
to hereditary diseases. The aforementioned advan-
tages of SNPs have all been successfully applied, and
SNP analysis occupies an unsurpassed position in
forensic practice. Thanks to ongoing research
advances, reliance on SNP testing to obtain DNA
ß2018 The Author(s). Published by Taylor & Francis Group on behalf of the Academy of Forensic Science.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
https://doi.org/10.1080/20961790.2018.1489445
FORENSIC SCIENCES RESEARCH, 2018
VOL. 3, NO. 2, 103–104
