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[2013] ZASCA 115
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Bokolo v S (483/12) [2013] ZASCA 115; 2014 (1) SACR 66 (SCA) (18 September 2013)
THE SUPREME COURT OF APPEAL OF
SOUTH AFRICA
JUDGMENT
Case No: 483/12
Reportable
In the matter between:
SANDILE
BOKOLO
...............................................................................
APPELLANT
and
THE
STATE
........................................................................................
RESPONDENT
Neutral citation:
Bokolo v S
(483/12)
[2013] ZASCA 115
(18 September 2013)
Coram:
Malan, Theron and Majiedt JJA and Van der
Merwe and
Zondi AJJA
Heard:
23 August 2013
Delivered:
18 September 2013
Summary: Evidence ─ weight to be attached to
DNA profiling. DNA profile of appellant not included in crime scene
samples ─
in any event no evidence of the probability of that
occurrence ─ probabilities on the facts pointing to innocence ─
conviction of rape set aside.
______________________________________________________________
ORDER
______________________________________________________________
On appeal from:
Western Cape High Court, Cape
Town (Hlophe JP sitting as
court of first instance):
1. The appeal is upheld.
2. The conviction and sentence are set aside.
______________________________________________________________
JUDGMENT
______________________________________________________________
VAN DER MERWE AJA (MALAN, THERON AND MAJIEDT JJA AND
ZONDI AJA CONCURRING):
[1] During the evening of 30 or the early morning of 31
October 2004 a four year old girl was brutally raped and killed. Her
father,
the appellant, and another person (accused 2) were tried in
the Western Cape High Court (Hlophe JP) on charges of the murder,
rape
and indecent assault of the child. The appellant was only
convicted on the charge of rape and sentenced to 15 years’
imprisonment.
Leave to appeal against conviction and sentence was
granted by this court.
1
[2] The evidence establishes the following relevant
facts. The girl lived in Harare, Khayelitsha with the appellant and
her mother.
Her mother bathed the girl during the morning of Saturday
30 October 2004, as she had on the previous morning. On both
occasions
the girl had no injuries and her mother noticed nothing
untoward. On the contrary, at around 18h00 on the Saturday the girl
was
happily playing in the street with other children, whilst her
mother was preparing to go to church. The girl wanted to go along
and
therefore accompanied her mother to the church, which is about a ten
minute walk from their home.
[3] The appellant was not at home at the time. He went
to work and afterwards, at about 15h00, went to a shebeen across the
street
from his home. He remained at the shebeen until approximately
22h00. He was then in such a state of intoxication that the owner
of
the shebeen requested a patron to take the appellant home. The patron
did so and the appellant went to sleep straight away.
[4] Whilst her mother and others were preparing
vegetables at the church, the girl played with other children in a
park. When the
mother’s work was done, she went to the
bathroom, accompanied by the girl. She left the girl in the passage
immediately outside
the bathroom. She heard the girl calling for her
and she assured the girl that she would be back shortly. However,
when she emerged
from the bathroom a few minutes later, the girl was
missing. This took place at approximately 22h00.
[5] The mother, her other daughter and others searched
for the girl in the churchyard and surrounding area but could not
find her.
She and her daughter then went home where they found the
appellant in a drunken sleep. The police were called and several
further
efforts were made to find the girl, but at approximately
08h00 on 31 October 2004 a message was received that the girl’s
body had been found next to some bushes approximately 1,5 km from the
church. The subsequent post mortem revealed that she suffered
multiple tears of the vagina and probably died of asphyxiation.
[6] Later that same morning Captain Kinnear of the South
African Police Service attended the scene where the body was found.
He
placed a clean sanitary pad on the private parts of the body in
order to retain any fluid emanating therefrom. He made use of tape
to
keep the sanitary pad in place. It is common cause that samples from
this sanitary pad were analysed for DNA at the Biology
Unit of the
Forensic Science Laboratory of the SA Police Service.
[7] In respect hereof the respondent presented the
evidence of Colonel Sharlene Otto, employed as chief forensic analyst
at the
Biology Unit. Dr C J J Oosthuizen testified in this regard in
the case of the appellant. In order to evaluate the evidence it is
necessary to refer to basic principles of DNA and the method of
genetic profiling used in this case. In this respect I derived
valuable assistance from the work
DNA in the
Courtroom: Principles and Practice
by Prof
Lirieka Meintjies-Van der Walt.
2
[8] Deoxyribonucleic acid (DNA) is the genetic material
that is passed from parent to child. There are two sets of DNA
molecules
in a human cell. One set is found in the nucleus of the
cell (nuclear DNA) and the other in the mitochondria thereof. In what
follows
I refer to nuclear DNA.
3
The DNA molecules found in the nucleus of a human cell
are the same in all cells of the human body. The DNA does not change
during
a person’s lifetime. Except for identical twins each
person’s DNA is unique.
4
[9] DNA is a double-stranded molecule composed of 46
sections termed chromosomes. A chromosome is a thread-like structure
that carries
genetic information arranged in a linear sequence. The
chromosomes are arranged in 23 pairs. One chromosome per pair is
inherited
from each parent. The 23rd pair of chromosomes determines
an individual’s gender and differs from the others. An
individual
always receives an X-chromosome from the mother and either
an X-chromosome or Y-chromosome from the father. Individuals with XX
in the 23rd pair of chromosomes are female and those with XY are
male. In what follows I concentrate on the other 22 pairs of
chromosomes, called chromosomes 1 to 22.
[10] Each of these chromosomes consists of linked base
pairs to form a ladder-like structure. The ladder is twisted into the
so-called
‘double helix’. The only difference between
people is that every person has a different sequence of the base
pairs
in the chromosomes. Every person could therefore be identified
solely by the sequence of his or her base pairs. But because there
are a staggering number of approximately three billion base pairs in
the DNA in each human cell nucleus, this is not practically
possible.
[11] Scientists have however developed methods in which
a small number of sequences of DNA are analysed at specific physical
locations
on a chromosome that are known to vary amongst individuals.
Such a physical location on a chromosome is referred to as a locus
(plural loci). These physical loci are referred to by codes. The
codes of most loci refer to their physical locations, for instance
segment 1358 of chromosome 3 is referred to as D3S1358 and segment
1179 of chromosome 8 is referred to as D8S1179, but there are
also
codes consisting of abbreviations of scientific terms.
[12] A gene is found at a particular locus on a
particular chromosome. An allele is each of two forms of a gene at a
particular
locus. At each locus examined a person therefore has a
pair of alleles, one maternal and one paternal. This pair of alleles
is
called a genotype. A pair of alleles may be identical if the same
allele was inherited from both parents. A set of genotypes at
two or
more loci form a DNA profile.
[13] In this case short tandem repeat (STR) profiling
was used. This form of DNA profiling is one of the most widely used.
It makes
use of the polymerase chain reaction (PCR) technique. This
technique simulates the process which takes place when DNA is copied
prior to the division of cells in the body and produces multiple
exact copies of the DNA at the specific locus to be analysed.
[14] An STR is a short sequence of base pairs which is
repeated numerous times in tandem. The number of repetitions varies
among
individuals. The number of repetitions is used to name an
allele, therefore five repeats of a sequence is called allele 5. As a
person has two alleles at each locus, an STR profile will for
instance indicate that the alleles at a specific locus are 15:15,
if
that allele was inherited from both parents or 15:16, if these
alleles were inherited from the respective parents. The system
used
by the SA Police Service determines alleles at 9 loci as well as
gender, as explained above.
[15] The DNA fragments produced by PCR is subjected to a
process called electrophoresis. This process produces a computer
generated
graph called an electropherogram. On an electropherogram
the alleles at each locus are indicated as peaks on a baseline. If
the
individual received the same allele from each parent, the
electropherogram of his DNA will indicate one peak at a specific
locus,
otherwise there will be two peaks. More than two peaks at a
specific locus indicate that the sample is a mixture of DNA. The
electropherogram
assigns allele names to peaks. An STR profile is
therefore a series of numbers that represent all the genotypes
detected for each
locus in a particular sample.
[16] The height of a peak on an electropherogram
corresponds with the quantity of DNA present. An electropherogram may
however also
indicate material not naturally present in DNA. This is
called an artefact.
[17] Evidence of DNA profiling may be of great
significance in a given case. It is important, however, that evidence
of DNA profiling
be viewed in proper perspective in each case.
[18] Evidence that the STR profile of an accused person
matches that of a sample taken at the scene or can be included
therein,
is circumstantial evidence. The weight thereof depends on a
number of factors. These include:
(i) the establishment of the chain evidence, ie that the
respective samples were properly taken and safeguarded until they
were
tested in the laboratory;
(ii) the proper functioning of the machines and
equipment used to produce the electropherograms;
(iii) the acceptability of the interpretation of the
electropherograms;
(iv) the probability of such a match or inclusion in the
particular circumstances;
(v) the other evidence in the case.
[19] Paragraphs (i) and (ii) speak for themselves.
Analysts provide interpretations of electropherograms referred to in
paragraph
(iii). The weight of such expert opinion (and of
conflicting opinions) depends on the extent to which the opinions are
founded
on logical and cogent reasoning.
5
[20] If the STR profile of an accused person in fact
differs from the profile retrieved from the sample taken at the
scene, even
in respect of only one allele, the accused person must be
excluded as a source of the crime scene DNA.
6
However, the converse is not true. Because only a
limited number of STR loci are analysed, an STR profile cannot
identify a person.
7
Therefore the weight to be attached to evidence of an
STR profile match or inclusion in the first place depends on the
probability
of such a match or inclusion occuring in a particular
population. Without such evidence the STR profile match or inclusion
means
no more than that the accused person cannot be excluded as a
source of the crime scene DNA.
[21] If the profile in question may be found in many
individuals, a match between the profile of the accused person and
the crime
scene DNA will have little or no probative value. This is
of particular importance where the crime scene DNA is a mixture,
which
increases the likelihood that the profiles of other members of
the population can be read into the mixture. On the other hand an
extremely rare profile will strongly point to the involvement of the
accused person. This essential component of DNA evidence is
usually
presented in the form of statistical analyses of a population
database. This is a complex topic that does not in this case
require
further elaboration than the following general remarks.
[22] First, the more loci are included in the profile
the less chance there is of another person adventitiously fitting the
profile.
8
Second, statistical calculations of this nature
generally make use of the product rule. This rule postulates that the
probability
of several things occurring together is the product of
their separate probabilities. It calculates the numerical probability
that
a particular profile may occur in a population or, in its
alternative form, the numerical probability that a person randomly
chosen
from that population will possess the same genetic profile.
The important point is that the results of these calculations are not
absolute.
[23] This brings into play the other evidence in a case.
I cannot conceive of a criminal case where there is absolutely no
other
relevant evidence or evidentiary material. This may range from
direct eyewitness evidence implicating the accused to circumstantial
evidence as mundane as the proximity of the home of the accused to
the scene of the crime. This may of course also include evidence
pointing to the innocence of the accused. In the final analysis this
evidence determines whether the guilt of the accused has been
proved
beyond reasonable doubt or not.
[24] Applying these principles to this appeal, the
undisputed evidence is that in respect of two samples or cuttings
taken from
the sanitary pad that was placed by Captain Kinnear,
electropherograms were produced in the manner explained above. These
two samples
were referred to in evidence as pad 1 and pad 2
respectively and for convenience I do the same. These
electropherograms show that
both samples contain a mixture of DNA.
According to Colonel Otto, the combination of alleles on the
electropherograms in respect
of both pads 1 and 2 reflect the DNA of
at least three males.
[25] The STR profile of the appellant is also not in
dispute. The alleles thereof at the respective loci coincide with the
combination
of alleles reflected on the electropherograms of pad 1
and pad 2, except for the appellant’s allele 22 at locus FGA.
Although
there is an indication (referred to in evidence as a little
block) at the relevant place on each of these electropherograms,
neither
reflects a peak labelled allele 22 at locus FGA. The alleles
on these electropherograms at locus FGA are in fact 20, 25 and 26 (in
respect of pad 1) and 21, 23, 24 and 25 (in respect of pad 2).
[26] Nevertheless the evidence of Colonel Otto was that
as a matter of interpretation of the electropherograms they indicate
allele
22 at locus FGA and that the STR profile of the appellant
could therefore be read into the mixture reflected on the
electropherograms
of pads 1 and 2. She said the following:
‘
M’Lord,
at that point FGA 22:25, you will see that there is not a clearly
marked 22 at FGA. A possible reason for this is
that FGA is a huge ─
is one of the largest, how can I put it, largest areas in the DNA
molecule, so obviously when you have
DNA donated by quite a few
people, you can actually lose some of your bigger fragments. So
although there is not a labelled 22,
we do have indications of DNA
being present where we would expect to see a 22, so we can actually
interpret it as such.’
[27] On the other hand the evidence of Dr Oosthuizen was
to the following effect. Because the height of a peak on an
electropherogram
is proportional to the quantity of DNA, alleles not
detected in a less enriched sample of DNA may be indicated as a peak
in the
more enriched sample thereof. Therefore a hint of DNA in a
less enriched sample, if it represents DNA, should constitute a peak
in the more enriched sample. A more enriched sample in this context
simply means that it contains a greater quantity of the DNA
than the
less enriched sample. Pad 1 in this case contains a greater quantity
of DNA than pad
2. Pad 1
is the sample more enriched with sperm and
therefore the electropherogram thereof presents a much clearer
picture than that of
pad 2. There is a little block on the
electropherogram of pad 2 that hints at DNA where one would find
allele 22 at locus FGA.
However, if that was DNA, it should have been
represented as a labelled peak and therefore an allele on the
electropherogram of
pad 1. In the absence of any other explanation,
it must be concluded that allele 22 cannot be detected at locus FGA
on the electropherograms
of either pad 1 or pad 2 and that the little
block is in fact an artefact.
[28] The court a quo preferred the evidence of Colonel
Otto to that of Dr Oosthuizen. The court based this finding
essentially on
three grounds. First, it said Dr Oosthuizen only gave
evidence in respect of the electropherograms and did not personally
examine
‘the specimen’, presumably referring to the
samples. Second, Dr Oosthuizen gave no evidence in respect of control
measures
in the laboratory as was alluded to by Colonel Otto and
third, that Dr Oosthuizen ‘never gave evidence relating to the
basis
of his conclusions’.
[29] None of these reasons bear any scrutiny. Neither
the examination of the samples nor the control measures used in the
laboratory
have any relevance to the issue on which the experts
disagreed, namely the proper interpretation of the electropherograms.
Colonel
Otto made it clear that her interpretation is based on what
is reflected on the electropherograms that she brought to court and
she did not say that there is anything on the originals thereof that
cannot be detected on the copies that were made available
to Dr
Oosthuizen. And it is clear from what I have said that the statement
that Dr Oosthuizen gave no basis for his conclusions,
is simply
wrong.
[30] In my judgement the evidence of Dr Oosthuizen
should in fact have been preferred to that of Colonel Otto. Properly
analysed
the evidence of Colonel Otto quoted above, which was the
only evidence by her on the point in issue, means no more than that
it
is possible that allele 22 at locus FGA may have been lost in the
mixture. It does not exclude the reasonable possibility that that
allele was never there.
[31] Dr Oosthuizen has a PhD in molecular human genetics
and is experienced in the interpretation of electropherograms. He was
an
objective witness who gave credit and made concessions when due.
Importantly, his opinion that allele 22 cannot be detected at locus
FGA on the electropherograms of pad 1 or of pad 2, is based on
logical and cogent reasoning. It is scientifically accepted that
a
sample more enriched with DNA will show a higher peak on an
electropherogram than the less enriched sample. It is not disputed
that pad 1 was more enriched with male DNA (sperm) than pad 2. Dr
Oosthuizen in evidence graphically illustrated this by comparison
of
the electropherogram of pad 2 with that of pad 1. This accords with
the evidence of Colonel Otto that semen was targeted when
the samples
were taken but that despite this there is a bigger component of the
victim’s female DNA on pad 2 than on pad
1. This quantitive
element of the interpretation of the electropherograms was not taken
into account by Colonel Otto. I find the
reasoning that led to Dr
Oosthuizen’s conclusion that allele 22 at locus FGA is not
present on the crime scene samples, convincing.
[32] For the reasons mentioned there is at the very
least a reasonable doubt as to whether the STR profile of the
appellant could
be read into the STR profile of pads 1 and 2. In any
event, even on the assumption that this could be done, there is no
clear evidence
on record as to the probability of that occurrence in
the particular population. In addition the probabilities arising from
the
facts point strongly to the innocence of the appellant. As a
result of the factual circumstances related above, the trial court
appears to have found that the appellant raped the girl before she
went to church with her mother on the day in question and that
she
was thereafter again raped by accused 2 and at least one other male.
This is highly improbable, on the evidence of the mother
of the child
and on the general probabilities.
[33] It follows that the appellant
should not have been convicted of rape and the appeal must therefore
succeed.
[34] In the premises I make the
following order:
1 The appeal is upheld.
2 The conviction and sentence are set aside.
_____________________
C H G VAN DER MERWE
ACTING JUDGE OF APPEAL
APPEARANCES:
For Appellant: C B Brand
Instructed by:
Legal Aid Board, Cape Town
Legal Aid Board, Bloemfontein
For Respondent: M O Julius
Instructed by:
Director of Public Prosecutions, Cape Town
Director of Public Prosecutions, Bloemfontein
1
Accused
2 was convicted on both the charges of murder and rape and sentenced
to an effective term of imprisonment of 28 years.
He was refused
leave to appeal by the trial court as well as this court.
2
Meintjies-Van
der Walt,
DNA in the Courtroom:
Principles and Practice
(2010).
3
Mitochondrial
DNA is maternally inherited and not unique to an individual.
4
Approximately
99,9 per cent of DNA in humans are in fact identical. This shared
DNA creates human characteristics that are similar
in all people. It
is the approximately 0,1 per cent of DNA that is not shared that is
different in every individual with the
exception of identical twins.
See Meintjies-Van der Walt supra at 3.
5
See
Michael & another v Linksfield Park
Clinic (Pty) Ltd & another
2001
(3) SA 1188
(SCA) paras 36 and 37;
Buthelezi
v Ndaba
[2013] ZASCA 72
(29 May 2013)
para 14.
6
This
is the evidence of both Colonel Otto and Dr Oosthuizen. See also
People v Brown
1991
Cal App 4
th
623.
7
Meintjies-Van
der Walt supra at 9.
People v Brown
supra at 629.
8
Dr
Oosthuizen, who was called by the appellant, conceded in evidence
that analyses at 9 STR loci plus the gender marker is sufficient.
In
the United Kingdom tests are performed for 11 loci, including the
gender marker. In the United States 13 loci are used as
well as the
gender marker. Prof Meintjies-Van der Walt relates that the inventor
of DNA profiling, Sir Alec Jeffereys, has suggested
that 15 to 16
loci should be used in England as a result of the size of the
database. See Meintjies-Van der Walt supra at 43-44
and 84.