快猫短视频

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鈥檚 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鈥檛
fluoresce under commercially available Wood鈥檚 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鈥檚 lamp in
the past, none of them could tell the difference. That was because the semen
didn鈥檛 fluoresce. 鈥淲e were shocked,鈥� says Santucci. She and her colleagues
tested further samples with two different Wood鈥檚 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鈥檚 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. 鈥淭he lamps
that are marketed as Wood鈥檚 lamps don鈥檛 seem to be doing the trick,鈥� says Carole
Jenny of Brown University in Providence, Rhode Island.

Michael Knight of Britain鈥檚 Association of Police Surgeons says that the
lamps are used in Britain to detect semen. 鈥淚 hope the ones we use are at the
right frequency,鈥� he says.