If the three judges of the Guardian/Piccadilly Press crime short story competition had had to choose a single winner, they would probably still be arguing the toss. Happily, they didn't: they were looking for the best 10 stories, to be published in book form in the autumn, and decided that a 2-1 majority would suffice to see a teenage would-be author into print. They even admitted an 11th story when the two contenders for the final slot proved difficult to separate.

The competition - to write a story of not more than 3,000 words on The Perfect Crime? - attracted some 500 entries. A team of editors from Piccadilly Press whittled those down to 45; the company's managing director, Brenda Gardner, then chose her favourite 19; and the three judges - crime writer Colin Dexter (the creator of Inspector Morse), novelist and former Doctor Who script editor Terrance Dicks, and children's author and illustrator Joanna Carey - had to make the final selection.

It was the third such competition - the previous themes were The Perfect Love Story? and The Perfect Journey? - and Gardner thought the entrants had found crime a tougher nut to crack. Dicks suggested a reason. "Crime writing calls for more plot," he said, "which is hard to do if you're a beginner."

There were two striking points about the 19 stories from which the judges had to choose: all but two were written by girls (80% of the entries had come from girls), and there was very little common-or-garden crime: no shoplifting; no car theft or joyriding; no assaults; no drug taking; not even any mobile phone theft. Again, Dicks thought he knew why: "That's real life, you see; this is fiction."

What the 19 stories did have, according to Gardner, was "amazing variety", and that is reflected in the winning 11 stories, which include two murders born of jealousy, a mercy killing, a family row that ends in death, a Mafia "hit", two peculiar killings in Roman Britain, a teacher arraigned for having sex with a pupil, a boy who thinks he has committed a murder because he told his best friend that he "wished he was dead" and 24 hours later he was, a con in the Australian bush involving a kangaroo, and a war between a cat and a dog.

It is tempting to say that all life is here, except that, as Carey pointed out, it is death that really preoccupies teenage authors. The murder of a young woman in Camden Town, killed by a stalker she imagines as a vampire, was extremely scary, and Sara Freeman's story of a jealous twin murdering (or perhaps attempting to murder - the ending is cleverly ambiguous) her sibling was grippingly told.

There were, as Dexter observed, few conventional whodunits, and those that made it to the final round were disappointing. "A short story works when it blossoms from one idea," he said, "and it's hard to do a whodunit as a short story." Most of the winning stories had one very strong, controlling idea - and perhaps a twist on the final page. Whodunits, by contrast, need a slower burn, lots of red herrings and a neat dénouement.

Dexter was critical of the way some of the stories were told, but impressed by the ingeniousness of many of the ideas. "The ideas," he said, in a crisp manner befitting a former teacher and examiner, "were often better than the execution." Dicks felt that if the story succeeded on one of the grounds - great idea or good writing - that would be sufficient.

The judges chose Laura Tobia's story - an elaborate con involving a kangaroo who plays dead to rob a Japanese tourist - because they loved the sting, which ended with the animal hopping into the bush wearing the tourist's red jacket and clutching his wallet. (The nature of the con, which Carey thought sounded like an urban myth, is tricky to summarise, so you will just have to buy the book.)

The judges' tastes were markedly different: Dicks disliked the two stories narrated by animals that made the final 11 - he called them "twee" - but Dexter enjoyed them, and Carey thought that Maire MacNeill's tale of a cat framed by a sly dog would be a useful counterweight to the gothic horror of the "vampire" murder and the apparent obsession with comas and mercy killings. Gardner said she was disappointed that there hadn't been more comic interpretations of the "perfect crime?" theme. Lighten up, out there.

One story all were agreed merited inclusion was Katherine Davidson's Love Letters. It tells the story of a young girl who gains revenge on a teacher who has humiliated her in class by tempting him into an affair and then exposing him. "Beautifully written, very controlled and with some clever asides - like the teacher who takes Wednesdays off in appreciation of French culture," said Carey. It was often those telling details that caught the judges' eye, as much as the big idea behind the story and the clever twist that many of the winning authors supplied.

Two of the winning stories had Roman themes, perhaps a hangover from the popular film Gladiator. Dexter thought Helen Whittaker's story, about a Celtic horse called Ruairidh, which kills the Roman who captures him, showed particular promise. He also liked Stephen Humphrey's ingenious story about a Mafia hitman, which made the final cut even though Dicks thought it a touch derivative of The Godfather. "I don't think we ought to worry that the stories might have been pinched from somewhere else," said the pragmatic Dexter, "or we'll never finish." Creative borrowing, not to be confused with plagiarism, certainly isn't a crime.

· The winners, in alphabetical order and with their age at the time of writing their stories in brackets:

Katherine Davidson (15)

Sara Freeman (14)

Stephen Humphrey (17)

Maxine Kocura (14)

Maire MacNeill (15)

Jenny Morgan (15)

Leanne Rutter (15)

Laura Tobia (15)

Abbie Todd (18)

Gemma Tomkys (17)

Helen Whittaker (15)