The Atomic Eye

In a California courtroom, an accused murderer will soon be confronted by a novel adversary. A witness for the prosecution will be an atomic scientist, armed with "radiation fingerprints," evidence that can be as accurate and reliable as a photograph of the actual crime. No ordinary cop could hope to gather such fingerprints, or even to decipher them. They are the product of neutron activation analysis, which requires that specimens under study be irradiated with neutrons in a nuclear reactor. Then the fine details of their chemical composition can be deduced from the pattern of the radiation they give off.

Though the technique is not new, it has never before been used in crime detection in the U.S.,* and with its astonishing sensitivity, it promises to provide law enforcement with an ultimate gumshoe.

Neutron activation analysis functions best as a reverse application of the common fingerprint technique--instead of gathering evidence a criminal leaves at the scene of his crime, it permits examination of evidence that the scene (or the weapon) leaves on the criminal. It can serve as an omniscient monitor of the most carefully planned alibis.

A cotton swab, for example, can be rubbed over a suspect's hand, irradiated, and its gamma rays studied to determine whether the man has fired a gun. Infinitesimal traces of gunpowder components left on the hand by explosion gases show up unmistakably under neutron analysis.

The sensitivity of the technique extends to one-billionth of a gram. It is a marvel at detecting the presence of poison, easily spotting a thimbleful dissolved in ten tank cars of water. Neutron analysis can get along with specimens far smaller than those needed for conventional chemical analysis: a fragment of lint, a strand of hair, a fleck of paint will suffice. Happily, the radioactivity caused by the neutrons soon dies down, and once studied, the evidence can safely be brought into a courtroom.

Neutron activation analysis has yet to be ruled on officially by a high U.S. court, but its backers are confident; the technique claims extreme accuracy--comparable to the best chemical techniques--and its sensitivity offers crime detection a powerful new weapon. Says Dr. Vincent Guinn, a radiochemist who is director of a joint project of the Atomic Energy Commission, General Dynamics Corp. and the Los Angeles police department: "Neutron activation analysis is no cure-all for crime, nor do I think it will replace regular chemical analysis procedures.

But it may well be a quantum change in the sense of enabling the investigator to identify materials with a degree of accuracy and sensitivity never before available to him."

* NAA evidence helped to win a 1959 murder conviction in Canada and has been used in French courts.

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