Scientific sleuths find clues in invisible details

By GREGG WYCHERLEY

The first clues will be fingerprints.

Then the forensic specialists will spread out, analysing the cyanide letters for clues about the photocopier that may have been used to duplicate the addresses on the front.

Next come the tell-tale signs left by every typewriter and photocopier. Every nick, mistake and odd flow of ink on the letter and envelope will be studied and recorded.

At the same time, scientists will examine the inks and paper under selected wavelengths of light or using coloured filters.

Slowly, the most mundane scraps of paper, ink and glue will reveal their secrets, hopefully helping detectives pin down the culprits.

Welcome to the closeted world of the scientists of the police Document Examination Unit.

The eight-member team, based in Wellington, analyses documents such as extortion notes and death threats and passes on its findings to police detectives, other Government departments and sometimes private investigators or individuals.

The unit's scientists can then present their findings in court, often providing the vital evidence police need to nail down their case.

The chief document examiner, Inspector Allan Herkt, said the scientists were trained in forensics to detect tell-tale clues overlooked by offenders.

"In forensic work any contact leaves a trace. You may well get a document or parcel with what appears to have nothing on it.

"But if there has been something there it will often come up under infra-red luminescence or infra-red reflectance."

Mr Herkt said he had expected to receive the envelopes and letters yesterday and begin examination immediately.

Examiners would try to determine the printing process used on the letters or envelopes, and analyse the handwriting and ink used in any written or printed material.

On the letter sent to the Herald, the address had been typed, photocopied, cut into a square and then glued on to the envelope.

"I'm expecting they will have been done and printed out perhaps on a laser printer and maybe then photocopied for the number of copies that were sent around," said Mr Herkt.

"But I don't know until we see it.

"We will be determining what printing process has been used, whether it's laser, ink jet, carbon or fabric ribbon."

He said analysts used a variety of methods and equipment to detect where documents had been fabricated using photocopiers, typewriters, and various types of printers.

Handwriting could be examined and compared with known samples of suspects' writing and typewritten and computer-generated documents were studied in an attempt to identify their source and date of production.

Latent writing indentations on documents could be visualised to determine if a document had received imprints from other documents.

Mr Herkt said the unit worked on between 400 and 500 cases a year, of which about 85 per cent were for police.

"Maybe 60 per cent of our reports will have information that I would regard as being useful to the investigation, which could be used in court."

He said that in double-blind trials of handwriting and signature analysis carried out by independent university testers, the unit had an error rate of only 0.4 per cent.

"Realistically there are only a few avenues you can go through to get to an offender. One is investigation ... then you've got things like fingerprints, maybe DNA and maybe indentation."

Police also rely on scientists from Environmental Science and Research - a one-stop forensic service, contracted to manage a databank of DNA samples, analyse illicit drugs, body fluids and physical evidence from crime scenes.

ESR spokesman Peter Wilson said scientists had given the police an analysis of the cyanide and could also test for DNA on letters if requested.