Missing clues

时间:2019-03-07 02:14:06166网络整理admin

By Nell Boyce POLICE doctors may be missing important evidence of sexual assaults and child abuse. Semen fluoresces under the right wavelength of ultraviolet light, but the lamps used in the US produce the wrong wavelength, say researchers. For decades, doctors have relied on a device called a Wood’s lamp to detect traces of semen on skin and clothes. But Karen Santucci of Yale University School of Medicine in New Haven, Connecticut, has discovered that semen doesn’t fluoresce under commercially available Wood’s lamps, which typically emit ultraviolet at wavelengths between 320 and 400 nanometres. Santucci originally set out to discover whether medical products, such as lubricants or ointments might give false positives. She tested the ability of 41 doctors to distinguish between various medical products and semen dabbed onto pieces of cloth. Although 25 said they had detected semen using a Wood’s lamp in the past, none of them could tell the difference. That was because the semen didn’t fluoresce. “We were shocked,” says Santucci. She and her colleagues tested further samples with two different Wood’s lamps, but saw no fluorescence. But the samples did fluoresce under wavelengths around 490 nanometres, so a different ultraviolet lamp could solve the problem. At the Yale-New Haven Children’s Hospital, doctors have already used such a lamp to obtain evidence that forced a confession from a man accused of raping a child. Experts on child abuse are worried about the results of the study. “The lamps that are marketed as Wood’s lamps don’t seem to be doing the trick,” says Carole Jenny of Brown University in Providence, Rhode Island. Michael Knight of Britain’s Association of Police Surgeons says that the lamps are used in Britain to detect semen. “I hope the ones we use are at the right frequency,