Lie detector tests should not be used as evidence in court because they are unreliable, and are "psychological torture" for the innocent, experts told METRO yesterday.
Qiu Baochang, one of the directors at the Beijing Bar Association and the director of Beijing Huijia Law Firm, said that according to Chinese law, lie detector tests can neither be considered as evidence nor as verification of evidence, because the technology is not accurate.
He said the environment in which the test is taken, and the emotions of the person being tested, can easily influence the test results.
The tests are not 100 percent scientific, he said, and so the results cannot be used as evidence in court.
"This especially applies to criminal cases where the evidence has to been proven exactly true," said Qiu, adding that lie detectors shouldn't be used, even when there is only a one percent chance of error.
It follows a report that Haidian prosecutors are using lie detector tests as an investigation tool for officials suspected of corruption.
According to the report, Xu Yongjun, a Haidian prosecutor, said it is hard to collect evidence for corruption cases because they usually involve just the briber and the bribe-taker.
Xu said these crimes are harder to trace than ever before and so lie detectors have been introduced as a way to establish whether suspects are telling the truth or not.
Mao Shoulong, a political science professor from Renmin University of China, said polygraph tests could be a form of psychological torture for people who are innocent.
"The nervousness caused by the test itself can make the results incorrect. It could make the truth seem like a lie. But for government officials who reek of corruption, the results may show that they are innocent if they know how to control their emotions," Mao said.
Mao said government officials in charge of real estate, construction of public facilities such as roads and buildings, and the allocation of land use, are most likely to be corrupted.
According to the report, Haidian prosecutors used a lie detector test in a corruption investigation involving a university professor. The suspect did not give away any information until he was asked to take a polygraph.
The suspect eventually admitted to corruption when faced with the test results, the report said.