Brick 'fingerprint' builds crime case: Steve Boggan on an academic breakthrough that helped to cement the conviction of the killer and kidnapper Michael Sams

IN 1892, Sir Arthur Conan Doyle - in referring to Sherlock Holmes - may have unwittingly written Detective Sergeant Tim Grogan's epitaph: 'It has long been an axiom of mine that the little things are infinitely the most important.'

DS Grogan's role in the conviction of Michael Sams for the murder of Julie Dart and the kidnap of Stephanie Slater is being celebrated this week by academics at Leicester University whose invention - brick fingerprinting - played a major part.

They were called in to help DS Grogan in the summer of 1991 after Sams used two white-painted bricks as markers along a trail leading to an abortive ransom drop for Julie Dart on the M1 near Barnsley in South Yorkshire.

At the suggestion of Andy Biggs, a brick technologist at the Steetley Brick company in Stoke-on-Trent, now owned by Redland Bricks, he called in Professor Ansel Dunham, the head of Leicester's geology department, who had helped develop a database on the composition of bricks.

'My gaffer wasn't too happy about me breaking up one of the bricks for the Leicester research because it was evidence, but I slipped a bit away while he wasn't looking,' DS Grogan said. 'I was convinced these guys could help, and they did.'

Professor Dunham was able to narrow down the clay used to make the bricks to just one quarry, Bradwell Wood at Newcastle-under- Lyme, Staffordshire.

Armed with details of the brick fingerprint, DS Grogan then had the bricks dated at about 20 years old by Doreen Stoneham, an archaeologist at Oxford University. The bricks were Staffordshire Blue engineering bricks known for low water absorption and strength.

He finally hit the mark when Mr Biggs traced pressing marks on the side of the remaining brick to Metallic Tileries, a brick manufacturer in Newcastle-under-Lyme, which ceased trading in 1977. John Rowley, who had owned the company, remembered making the batch for Wettern Brothers in Kent, which later sold out to Ready Mixed Concrete. Wettern's records finally showed that a batch had been sold to Blighton and Clarkson, a firm of builders in Newark, Nottinghamshire. Jamie Clarkson, the former owner of the firm, also remembered the batch.

In January 1992, Stephanie Slater, an estate agent, was kidnapped. A tape of the kidnapper's voice on the BBC's Crimewatch was recognised by Sams' wife, who turned him in.

A short time later DS Grogan received a call from DS Mick Shilleto, a close colleague who had been searching Sams' workshop in Newark and another he used to occupy in Peterborough. 'Mick said he had found three of the batch we had identified. One had been broken into two halves and was supporting a bookshelf in the Newark workshop, and two more were found in Peterborough.'

More tests showed the bricks were all from the same batch, showing that Sams was responsible for Julie Dart's kidnapping and murder and for Stephanie Slater's kidnapping. 'Sams probably stole the bricks from Mr Clarkson's yard in Newark, which was very close to his workshop,' DS Grogan said. 'We had actually got to within yards of him with nothing more than two bricks.'

(Photograph omitted)