Making the invisible visible

ESR scientist John Buckleton helped develop the new technique. Picture / Dean Purcell

A dramatic DNA advance with the potential to solve crimes when there is no apparent evidence is about to be launched in New Zealand.

Because it opens the possibility of retrieving an offender's DNA from a sample that can't be seen by the naked eye it has been billed as heralding "the invisible sample".

The technique was the evidential tool that cracked the case of British traveller Pete Falconio, murdered in the Australian outback.

Falconio, 28, and his girlfriend Joanna Lees were in their orange Kombi campervan hours north of Alice Springs five years ago when they were flagged down by the driver of a white four-wheel drive truck. Lees told of hearing what sounded like a gunshot after her boyfriend went to the rear of the camper to talk to the man who had stopped them.

The case details are well known: how the stranger tied Lees' hands and put her in his truck, how she made a run for it and hid in the spindly bush for hours before waving down a truck, how Falconio's body has never been found. That last fact gave rise to speculation that things might not have been as Lees described.

But the ties Lees said were used to bind her were sent to the United Kingdom's Forensic Science Service which with input from New Zealand forensic scientist Dr John Buckleton pioneered the highly-sensitive process called low copy number (LCN) DNA.

Advances in forensic use of DNA have involved developing techniques which amplify the available DNA for analysis. DNA is a double helix which, through heating and cooling, can be made to separate and re-form. By adding other measures, the DNA duplicates. Each cycle the DNA is put through potentially doubles it.

LCN puts it through 34 cycles compared to 28 for the standard method (called SGMplus). Though the difference between the numbers doesn't seem much, it involves a 50-fold increase in sensitivity and potentially makes the invisible visible, the undetectable detectable.

Using LCN, British forensic scientist Jonathan Whitaker obtained a DNA profile from deep inside the homemade ties used to bind Lees. The profile matched Bradley Murdoch, a self-confessed drug runner.

Whitaker testified that the DNA profile from the ties was 100 million times more likely to have originated from Murdoch than any unrelated person. That evidence was supported by what scientists call a partial match where fewer clear DNA results are obtained from the sample and the match is therefore assigned a lower numerical certainty.

The partial match was from a swab taken from the Kombi gear stick which Murdoch touched when he drove the camper off the road to hide it. Murdoch is appealing his conviction.

Whitaker also gave evidence in the first New Zealand case to use LCN DNA evidence (see story below) and has been here to help the Institute of Environmental Science and Research (ESR) prepare to begin using the technique from December.

Ten years ago a large bloodstain, the size of a 50 cent coin, was thought to be the minimum for successful DNA analysis. Improved techniques meant a mere smudge, such as a nose-print left on a window could give a DNA result that led to an offender. Now LCN technology opens the door to the realm of the invisible. In Britain, the technique has generated DNA profiles from items such as tools, matchsticks, weapon handles and clothing the offender has grabbed.

The bogey is contamination. The very sensitivity of the technique which enables it to extract a DNA profile from the tiniest sample also makes it extremely vulnerable to contamination. Stringent measures are needed to minimise that risk.

The ESR has spent $1 million building special anti-contamination areas at its premises in Auckland, Wellington and Christchurch. Protocols are being developed for crime scenes where the LCN technique is used and for the handling of samples from collection through to courtroom.

LCN crime scenes will be divided into cold, warm and hot zones hot being the crime zone. Clothes are put on and discarded at each zone to minimise the risk of contamination.

We live in a "soup" of DNA, explains ESR forensic programme manager Keith Bedford. "If I were to shed dandruff, massive amounts of dna could fall ... hair could carry DNA. The way I am speaking at the moment, we could probably detect DNA on this pad in front of me."

"LCN is not just about turning up the dial in the DNA lab, or about a tweak to the DNA system," says Bedford, "it is a reworking of the the whole process."

Scene examiners and sample analysts gown up like surgeons, dressing down from hairnet to booties to avoid, for example, a dislodged hair falling on to the gown.

Consumables, such as the water used to dampen swabs, must be DNA free.

Back at the laboratory, there are a range of measures from sticky mats to remove material from footwear to special fluids and ultra-violet light for cleaning the sparse examination area which has separate air conditioning to avoid contamination from air elsewhere in the building.

At the ESR's Auckland premises, entry to the LCN examination area is restricted to three specialist analysts and an equipment calibration technician. It includes a dressing lobby and a sampling room with a "biological safety cabinet" in which the sample is placed inside a tube that in turn is certified by its manufacturers to be free of DNA.

The tube containing the sample is taken to the next sealed area where chemicals are added as part of the process of extracting a DNA reading.

As an aid to accounting for extraneous DNA, people who come into contact with the scene or sample through their work (scientists, police, emergency service staff, pathologists) will have their DNA stored on a special register.

British analysts were puzzled when the new technique turned up the same DNA profile from samples taken from the scenes of three very different types of crimes. The prospect of it being the DNA fingerprint of a most versatile criminal was extinguished when it proved to be the DNA of an employee of the German manufacturer of a piece of equipment used by the scientists.

The British have used LCN DNA in volume crimes, such as blitzes on car theft rings, but because the process takes longer and is more expensive than the standard method, it is likely to be reserved in New Zealand for serious crimes that conventional investigation techniques cannot solve.

Bedford expects LCN will be used in about 50 of 1000 cases handled annually by the ESR's priority crime team. "That's a significant increase on what we have been able to do by referring cases to [Britain]," he says. "Unfortunately because of the expense it's been a technique of last resort."

The police and ESR are reviewing cold cases to find those suitable for LCN analysis.

Bedford: "It involves a lot of work but [LCN] is a big jump forward."

Earlier advances in DNA have resulted in convictions long after the crime 16 years later for the killer of Napier schoolgirl Teresa Cormack (caught from a trace of semen), 17 years for the murderer of Queenstown woman Maureen McKinnell (caught from tiny amounts of skin and blood lodged under her nails).

"LCN is going to be a major tool for us, a significant weapon in our investigative armoury," says John Manning, a former detective inspector who is the police's liaison with ESR. It will lead, he says, to quicker resolution to some serious crimes and enable police to resolve some old cases.

"This is likely to mean that rapists and other serious criminals who might believe they have got away with their crime are in for a significant surprise." It won't, however, be a panacea. DNA is most powerful when supported by other evidence.

Manning won't specify cases that will be revisited, as much because he doesn't want to raise victims' hopes as for tactical reasons. "We are confident that we will identify a significant number of cases that will be suitable for forensic review and if the experience in the United Kingdom is any guide we again would be confident that would led to a good percentage of those being resolved."

Protocols on crime scene practise regarding LCN are being finalised and training planned in all 12 police districts. Judgments will need to be made early, Manning says, about designating a serious crime an LCN scene and setting up the necessary anti-contamination measures.

LCN DNA is potentially as useful in clearing a suspect or wrongly convicted person as it is in leading police to the offender. David Dougherty was freed after DNA proved the semen on the rape victim's underwear was not his. But it was a long, lonely battle.

Advances such as LCN are less likely to lead to the wrongly-convicted being cleared in New Zealand than the UK because we lack an authority dedicated to investigating possible miscarriages of justice. Currently, people claiming to be wrongly convicted can appeal through the courts, or seek a pardon through the Justice Ministry.

In January retired High Court Judge Sir Thomas Thorp, who estimates that 20 people may be wrongly imprisoned, recommended an independent authority with its own investigative capability to be set up to identify miscarriages of justice.

The Government said it intends to give his report "careful consideration" but has not indicated how or when. Law Commission president, former Prime Minister Sir Geoffrey Palmer told the Weekend Herald Sir Thomas had raised "a serious issue and it cannot be ignored."


The sensitive way to catch a rapist

Joseph Warren Lepper might have thought he was home free because of his foresight in wearing a condom when he went raping one morning in May of 2002.

The condom lessened his risk of being caught by his DNA.

Lepper would not have known about a new technique which enables forensic scientists to detect DNA profiles in samples so tiny they are invisible to the naked eye.

His case is believed to be the first to include the DNA profiling technique - called LCN (low copy number) DNA - as evidence in New Zealand.

The hyper-sensitive forensic DNA technique may revolutionise criminal investigation and could also be an effective tool for identifying miscarriages of justice.

New Zealand scientists will be using the technique by the end of the year, but LCN DNA evidence was included in the case against Lepper when two semen stains were sent to England, where the technique was introduced in 1999, after the standard technique used here failed to gain a DNA profile.

Lepper was convicted of abducting a 54-year-old Palmerston North woman out on her morning walk, and dragging her into a park where he raped her.

As well as wearing a condom, Lepper scuffed the ground where the rape occurred in an attempt to cover any trace of what had happened.

The case hinged on the analysis of DNA found in a speck of semen in soil from the scene and in semen stains in the arch of one of the women's shoes and the waistband of her underpants.

Britain's Forensic Science Services extracted DNA profiles from the two samples. They matched each other and also the DNA profile extracted by the ESR using the standard less-sensitive method. All three matched Lepper's DNA.

Having earlier denied even knowing the existence of the park where the rape occurred, Lepper then claimed his semen was found in those samples because he had had consenting sex with another woman in the exact spot shortly before the rape. The jury rejected this.

Then, in the Court of Appeal, Lepper challenged the LCN technique claiming that it was so new that the jury had no means to assess its reliability, and raising the possibility of contamination.

In dismissing the appeal, the three judges said the defence had had adequate scope to question LCN's reliability at the trial and that they saw no basis for concern regarding contamination.