An unsolved murder mystery, a 20-year-old arrest warrant and a potentially calamitous slip on the chief suspect's blog threaten to plunge the Japanese criminal justice system into crisis.

The surprise arrest in Saipan of Kazuyoshi Miura, a 60-year-old clothes importer, could, lawyers say, expose a string of failures that stretch from Japan's blunder-prone police to the Supreme Court.

Mr Miura and his 28-year-old wife, Kazumi, were shot in a Los Angeles car park in November 1981. He was hit in the right leg, while she was shot in the head and died in a Japanese hospital a year later.

The media went wild with the story of a young businessman and his wife coming to grief on the mean streets of Los Angeles.

Then doubts surfaced. Mr Miura, it seemed, had a strikingly beautiful mistress and his wife had a strikingly hefty life-insurance policy. Later, evidence emerged that, before the shooting, Mr Miura had arranged for a friend to attack his wife with a hammer in her hotel.

Tried in Japan for murder, Miura was found guilty by the Tokyo district court, but the judgment was overturned by both the High Court and Supreme Court, largely because there was no traditional confession by the accused - the nation's preferred method of achieving convictions. It took Japan's notoriously unhurried legal system nearly 22 years to reach that decision.

After serving a sentence for attempted murder, Mr Miura began to travel again, but made the mistake of describing his holiday plans on his blog. When the LAPD learnt that Mr Miura would be setting foot on US commonwealth territory on a visit to Saipan, its officers swooped.

To further expose the flaws in the Japanese prosecutors' case, the LAPD said yesterday that it was confident that old evidence gathered before 1988 was sufficient to secure a conviction. As a result, the criminal justice systems of Japan and the United States are to go head-to-head, processing the murder case with exactly the same evidence.

The potential for embarrassment is considerable. Japan is wrestling with its dual demons: the introduction of jury trials from April next year and whether to record police interviews with suspects.

The latter is now the subject of acrimonious debate. The police reliance on “confessions in camera”, and Mr Miura's maintenance of his innocence, could now be exposed as the more evidence-based US justice system processes the trial this year.

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