USE OF DNA TYPING FOR CRIMINAL CASEWORK IN SRI LANKA

USE OF DNA TYPING FOR CRIMINAL CASEWORK IN SRI LANKA
Nalin C.W. Goonesekere, Ph.D., Maya B. Gunasekera, Ph.D., and Neil Fernandopulle, B.Sc.
Department of Chemistry, University of Colombo, Sri Lanka.
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Sri Lanka is a small island of 17 million people, situated in the Indian Ocean.  It is a member of the
Commonwealth of Nations, and its system of justice has elements of both English Law as well as Roman
Dutch Law.  There has been no special legislation enacted specifically to deal with DNA evidence.  Under
the current laws of evidence, blood samples can be obtained from suspects for DNA typing, provided
prior consent is obtained.  However, it is possible to obtain a buccal swab, or hair samples, without
consent from the suspects.
We began our work on DNA typing in Sri Lanka in 1996, due to the considerable public interest in this
field.  The reason for this is that apart from its relevance to routine criminal investigations, DNA typing can
also be applied to identify victims in mass graves, and victims of bomb blasts.  We selected the short
tandem repeat (STR) method
1
 of DNA typing, because it has the twin advantages of high sensitivity, and
the easy assignment of alleles.  Further, this method does not require the use of radioactive chemicals,
and is also technically less demanding than methods based on minisatellites.
We began by establishing population databases for some selected STR markers through a research
grant from the National Science Foundation of Sri Lanka.  The STR markers we selected included the
CTT system, the FFv system and the Silver STR system (Promega Corporation, U.S.A.).  While we were
engaged in our research project, a particularly gruesome mass murder took place in Sri Lanka shocking
the entire nation.


On February 10, 1999, in the village of Hokandara in a suburb of Colombo, six members of one family
comprising the father, mother, three daughters, and a son were brutally murdered.  The perpetrators had
used a variety of weapons including knives, iron bars, and an axe.  One of the alleged murderers was
also found dead at the scene of the crime.  Based on previous records of a land dispute, three suspects
were arrested the same day.  All three suspects were found to be wearing blood stained clothing at the
time of the arrest.  These items were immediately removed and stored as evidence by the police.  Several
strands of hair were also recovered from one of the suspects.  The police report also indicated that one of
the victims may have been raped.  However, no vaginal swabs had been taken.  The case against the
suspects was based entirely on circumstantial evidence as there were no eyewitnesses and no direct
evidence for the presence of the suspects at the scene of crime.
It was under these circumstances that the police sought our assistance, through a court order, to DNA
type the blood stains and the hair samples found on the suspects clothing, weapons and compare them
to body swabs, blood stained clothing and hair samples of victims obtained during the autopsy.  We
received the samples exactly two weeks after the murder.  During this time, the samples had been kept at
room temperature (31
o
C) under ambient humidity (80% relative humidity).  In addition, we received blood
samples from all three suspects, collected with their consent.
The evidentiary material was subjected to STR typing by multiplex PCR (GeneAmp 2400, Perkin Elmer,
U.S.A.) at nine loci described above.  Briefly, DNA from bloodstains were extracted using the chelex
procedure
2
and PCR amplified
3
, while the hair samples were boiled directly in the PCR buffer
4
 before
amplification.  PCR products were analyzed by polyacrylamide gel electrophoresis and visualized by
silver staining
5
.  The DNA profiles obtained are given in Table 1.Table 1:  Case DNA profiles for Nine STR loci

1.  The entire hair sample was used for one multiplex (FFv) reaction.
2.  CTT loci could not be typed; Silver STR loci were not subjected to typing.
3.  Silver STR loci were not subjected to typing.

Discussion:
Bloodstains from the clothes of all three suspects were successfully typed at all nine loci, and all revealed
an identical pattern, indicating that the blood was from one individual.  An identical DNA profile was also
observed for one of the victims (the son).   Thus, the DNA evidence was supportive of the conclusion that
the bloodstains found on the clothing of all three suspects came from one of the victims.  When the single
hair root, obtained from the clothes of one of the suspects was typed at the FFv locus, the DNA profile
obtained was identical to the DNA profile of one of the victims (daughter).
Body swabs of victims taken at the autopsy by the Judicial Medical Officer (using gauze bandage
material) did not yield successful PCR amplifications.  The blood stains present on the clothes of the
mother, and the daughters appeared to be “diffused” possibly indicating contact with water.  These blood
stains amplified poorly.  There were no bloodstains present on the clothing of the father.  The son’s
garments, which contained most amount of blood, and had patches of well dried blood spots, amplified
well.  The suspects clothing contained small well dried patches of blood, mainly on the front side.  All
such stains that were subjected to PCR amplified well, and were readily typed.  Due to financial
constraints, all bloodstains were not subjected to DNA typing, and the Silver STR system was used only
when deemed necessary.  None of the bloodstains obtained from the weapons could be successfully
typed at any of the loci.  This is the first report on the use of DNA typing for forensic casework in Sri
Lanka.References:
1. Edwards, A., Civitello, A., Hammond H.A. & Caskey, C.T. (1991). DNA typing
     and genetic mapping with trimeric and tetrameric tandem repeats.  Am. J.
     Hum. Genet. 49, 746.
2. Walsh, P.S. & A. David. (1991).   Chelex 100 as a medium for simple extraction of DNA for PCRbased typing from forensic material.  Biotechniques 10 (4): 506-513.
3.  Promega Technical Manual (1993) Part # TMD004, Promega Corporation, U.S.A.
4.   Hartl, G.B., Kurt, F., Tiedemann, R. Gmeiner, C., Nadlinger, K., Khyne, U. &
      Rubel, A. (1996). Conservation genetics and systematics of Asian elephant
      (Elephas maximus): A study based on sequence variation at the Cyt b gene
      of PCR-amplified mitochondrial DNA from hair bulbs. Z.Saugetierk. 61:285-
      294.
5.  Promega Technical Manual (1993) Part # TMD005, Promega Corporation,
      U.S.A.