Finding the survivors among the wreckage of a bombing or plane crash is difficult at best, so when the US government learned about a new device from DielectroKinetic Laboratories LLC of Washington, they were eager to put it to the test. What they discovered, however, was that the LifeGuard -- a virtual divining rod for human detection -- performed no better than random chance. According to company literature, the instrument operates on the principle of dielectrophoresis: It points toward a low-frequency electric field generated by the human heart. A 640-nm diode laser maximizes the flux density of this field so it can travel through barriers that absorb or reflect higher-frequency energy, such as concrete walls, steel bulkheads and up to 10 ft of water. The US Department of Energy called on researchers from Sandia National Laboratories to conduct a double-blind test of the LifeGuard, which has a list price between $6000 and $15,000. The researchers set up a row of five large plastic packing crates that were placed 15 m from the instrument, well within the published 20-m range of the Model 2. The task was to determine which crate contained a live human. An unnamed manager from DielectroKinetic Labs served as the instrument operator. Formal test protocol First, the team conducted a noncontrolled test where the operator knew which crate contained the human. In this scenario, he quickly guessed correctly 10 times out of 10. When he didn't know where the human was located, the operator had a one-in-five probability of success by chance alone. Under these conditions, Sandia researchers said the operator took a much longer time to scan the crates, and then guessed correctly only six times out of 25 trials. The conclusion: The results of the tests were consistent with random chance. The instrument operator maintained that the sharp edges of the crates distorted the field. Other representatives from DielectroKinetic Labs contended that the testing failed because the device is designed to detect the presence of a living person and provide only "some localization." Officials at the firm said they are conducting their own independent testing, the results of which will be available soon.