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.