A former top forensic scientist has traded a lab coat for a barrister's gown to defend the people her work once helped to put behind bars. Donna Chisholm, New Zealand Listener.
February 21, 2002. It's 5.30pm and in her third-floor office at the Institute of Environmental Science and Research in Mt Albert, Auckland, forensic scientist Sue Petricevic has one more job before she can leave for the day: examine a spreadsheet of the latest results of tests comparing the DNA of hundreds of Hawke's Bay men against that of the offender whose semen was found on murdered six-year-old Teresa Cormack in June 1987.
It has been 11 disheartening months since the screening samples began arriving at ESR after Petricevic extracted the DNA profile from the semen sample that had been stored for 14 years waiting for the technology to advance sufficiently to test it, knowing that a failed attempt would destroy it – along with the last chance to identify the killer.
More than 800 men have already given blood or hair samples and have been eliminated as suspects. Today's spreadsheet contains the next batch of 50 results – each containing numbers that must correspond to the eight sites on the offender's DNA.
Petricevic is tired and beginning to lose hope. "It was gruelling because there were so many samples coming in and nothing was matching. After 800, you start to think are you ever going to find this person? Are they dead? Are they overseas? Have we got any chance of finding him, it's a needle in a haystack. What happens if we don't find him?" Then she comes to "reference sample EK29" of man 845.
"I remember seeing the first couple of numbers matching, then the next couple matching, and the heart starts racing." When all the numbers align, Petricevic checks and then rechecks, unable to believe what she is seeing, before racing down the stairs to her boss' second-floor office. "We've got a match. We've found him," she says. Then she bursts into tears.
It was, she told the trial of Cormack's rapist and killer Jules Mikus, 60 million times more likely that the DNA came from him than another random New Zealand man. The jury was out just two hours before returning its guilty verdicts.
Fast forward nearly two decades and Petricevic has exchanged her lab coat for a barrister's gown as she prepares to defend offenders like Mikus and others charged with crimes from the mundane to the monstrous. After being a key expert witness for the Crown in horrific cases such as the 2001 RSA murders in Auckland, where she found killer William Bell's DNA on cigarette butts, and the 1996 hammer killing of Tania Furlan, in which she analysed blood spatter evidence (although Furlan's suspected killer committed suicide in prison before trial), Petricevic says she's now finding the job of advocating for suspects more rewarding.
It's understood to be the first time in New Zealand that a forensic scientist has made such a career shift and it comes as defence lawyers themselves begin to question whether they have the scientific nous to know when and how to push back against the increasingly sophisticated forensic testing that can strongly sway – or bamboozle – jurors. Petricevic has particular expertise in the increasingly important "trace" DNA that can be left on a surface by just a touch. In 2004, she spent nearly a year on an ESR fellowship to the laboratory of the French police, where she researched the retrieval of foreign DNA transferred by touch to the skin.
After gaining her law degree in 2006, Petricevic worked as a Crown prosecutor until 2014, and then spent four years prosecuting health and safety cases for WorkSafe before switching to the defence just over a year ago.
"I think you can be a more balanced lawyer if you've worked for both sides, and the prosecution can be quite a sanitised world – you don't interact with clients. There is a moment when you think, 'I wonder what it's going to be like dealing with people charged with these really serious crimes', but we're all people and the poverty and social factors are just huge when you start getting involved in it. Someone the other day couldn't afford transport to court so walked to Manukau from Papakura and the court nearly issued a warrant to arrest because they were late. A lot of my clients can't read but don't want to let on and they pretend they can, so you have to be quite careful. That's come as a shock to me because I thought it was rare."
She also recognised the need for specialised forensic knowledge on the defence bar.
"There's a lot of resource coming through on the Crown side but very, very little on the defence side. Most of it is funded by legal aid, and that requires that people know what they need to find out, and how to go about it, before they can even apply for funding, let alone find someone with the appropriate expertise."
Already, she is seeing plenty of cases where she believes the forensic science needs to be more closely examined. "Often, there is a lot more hidden information that you need to find, and you need to know where to look. Even things like knowing how a police investigation works, which forms should be on file, where is a certain form that I would expect to see, where is this chronology or notebook entry or witness – why haven't they been spoken to. It's what is missing, and the repercussions of that, that can be important. Police do a great job under a system that is stressed, but criminal procedure requires pleas to be entered quite quickly, so defendants may not have the full information and know the whole case against them – and that's a basic right."
It has been harder than she imagined to get some information. "I can see why defence counsel get frustrated, because it's difficult to get all the disclosure, although it's sometimes just a matter of police time and resourcing."
Can I help you, Mr Mikus?
So what would she say to a Mikus-like suspect who came to her when the DNA evidence was seemingly overwhelming? "I can't give away all my secrets!" she says with a laugh.
"You'd have to say the options are that either it's a mistake or it got there some other way. The chances of both are pretty remote, but I would always check the file to make sure everything was in order in terms of the custody of the samples, tests undertaken, what else could be examined, and look for evidence of contamination, mistakes or mix-ups."
Her critical advantage, she says, is that she understands the highly technical reports, can read them quickly and knows immediately what information is missing and what extra material may need to be sought.
It's difficult to imagine a more stressful job than that of forensic scientists who, when not analysing and interpreting crime-scene samples, are at the grisly scenes themselves. Petricevic has seen a butchered baby and women who've been bludgeoned or stabbed to death. She coped with the distress by focusing on the job. "There is no point being there if I can't do my job well. Sometimes, afterwards, I'd just want to go home and have a long shower or a walk to remove myself from it. It's never pleasant, but the way around it is to say, 'Something terrible has happened, but I'm here to help.'" She rolls her eyes at the TV shows depicting the job; says she never watches.
Being an advocate for the accused also brings its stresses. "At crime scenes, it is the horror of what you are seeing and being responsible for the evidence. In the cells, the stress is being able to connect with the person you are representing and doing the best job for them."
Petricevic has come a long way from the high-school leaver who wanted a career in science after seeing a newspaper photo of a white-coated figure taking an impression of a shoe print at a crime scene. She started at the then DSIR in 1981, testing fluoridated or chlorinated water samples, before moving on to wine and food analysis, drug testing and visiting clan labs when home-bake heroin first appeared. She began taking law papers part-time to improve her evidence in court, before seeing it as a career option.
She moved into crime-scene examination and DNA work in the early 1990s and says the identification of trace DNA has been a particularly exciting development. "I had groups of research students over the years and suddenly we could identify who was wearing a pair of shoes from the DNA left inside." Once, she says, she extracted a DNA profile from the pocket of a long-deceased man's brown woollen overcoat so that relatives could discover if they were at risk of inheriting a genetic disease.
Since her career shift, she's noticed defence counsel seem to be treated with suspicion by some police, something she finds remarkable. "I am still the same person, just working in a different role." Though she hasn't yet had a high-profile case to defend, she's looking forward to the opportunity and the chance of subjecting her former colleagues to "rigorous" cross-examination. "It doesn't have to be a full-on attack, but just a thorough examination of the evidence to get concessions from the witness."
Although the public expresses outrage at those who defend people charged with the most heinous crimes, Petricevic and the rest of the criminal bar argue everyone is entitled to a defence. And if someone like Jules Mikus turned up and asked for her to defend him, she would. "I think the lawyers who do those cases are very strong and courageous and that's good – because everyone is entitled to defend the charges against them. And, of course, sometimes we'd like to think we are helping the innocent as well as the guilty, but innocent until proven guilty is a fundamental right."