Lie detector’s reliability is under the microscope
Published: 15 Jan. 2010, 20:37
In the movie “The Case of Itaewon Homicide,” the lawyer (played by Oh Kwang-rok) suggests a lie detector test in order to prove his client’s innocence, thinking that the prosecutor (Jeong Jin-young) will give up his conviction that American citizen Alex ? his client ? is the culprit.
But the test ends up showing that Alex has lied. Alex is sentenced to life imprisonment at the first trial.
This may be just a movie, but whether a defendant is telling the truth or not is often a key point when there is little other evidence in a crime. In such incidents, a lie detector test is frequently suggested. The tests use a machine called the polygraph that analyzes breath, perspiration, pulse, and blood pressure in trying to discern whether the subject is lying.
There were 2,719 people who took the tests in Korea in 2008, and 1,715 people from January to June last year, a 40 percent increase over the same period the previous year.
Yet the polygraph has been dogged by controversy since its invention in the early 20th century, with most scientists agreeing it is nothing more than an interrogation technique subject to the biases of the examiner. Park Jeong-kyo, a court-appointed lawyer in Jeonju, North Jeolla, agrees. He recently wrote, “Investigative agencies use the untrustworthy lie detector tests in order to pressure criminal suspects,” in an article in a newspaper published by the Korean Bar Association.
“Although many defendants ? thinking they’re innocent ? trust a lie detector and easily respond to the request to take a test, it’s very hard to pass,” he commented. “If the result of the test turns out to be a ‘lie,’ most suspects will be indicted despite their claims of innocence.”
The Public Prosecutors’ Office wrote a rebuttal in the next edition of the same newspaper. “A lie detector is measured to be 92-percent accurate according to an academy in the United States,” wrote Ji Hyung-gi, director of the Psychological Analysis Department of the Supreme Public Prosecutors’ Office. “It also acts to prove one’s innocence,” he added. “The test results and the courts’ verdict matched around 81.3 percent of the time, and the court recently started to take notice of past research and results.”
Park then published a second challenge. “The investigative agency may take pride in a lie detector’s accuracy of over 90 percent,” he wrote. However, even if one were to grant the accuracy of that percentage, he argued, “the other 10 percent can produce a guilty verdict for an innocent defendant.
“I’ve seen many test results that showed both plaintiffs and defendants were lying.
In a phone interview, Park elaborated on his crusade. “I wanted to illustrate habitual practices done by some government agencies that utilized incorrect test results in order to induce a false confession. If the defendant rejects a request to take a test, [prosecutors] should not record the rejection as if it implies guilt.”
Ji at the prosecutors’ office responded, “We are prepared to prove how scientific and rational a lie detector test is to not only lawyers but also to the media.”
The Supreme Court of South Korea has not fully recognized the admissibility of lie detector tests. One ruling in a hit-and-run trial in May 2005 said, “A lie detector test lacks accurate measurability, rational questions or methods and objective interpretation ability,” acquitting the defendent. Academics also have concerns.
“If the public aversion to the concept of a machine judging a human being disappears, its results would be admitted in court,” said Lee Wung-hyuk, a professor at the Korea National Police University. He said a lie detector test is the second only to genetic evidence in its accuracy.
Still, Lee Duk-hwan, professor of chemistray at Sogang University and a member of the advisory committee on police equipment at the National Police Agency, said, “The physiological changes detected by the test depend not only on lies but also on personality or testimony. Technology at the present time cannot perfectly distinguish such differences.”
By Choe Sun-uk [[email protected]]
But the test ends up showing that Alex has lied. Alex is sentenced to life imprisonment at the first trial.
This may be just a movie, but whether a defendant is telling the truth or not is often a key point when there is little other evidence in a crime. In such incidents, a lie detector test is frequently suggested. The tests use a machine called the polygraph that analyzes breath, perspiration, pulse, and blood pressure in trying to discern whether the subject is lying.
There were 2,719 people who took the tests in Korea in 2008, and 1,715 people from January to June last year, a 40 percent increase over the same period the previous year.
Yet the polygraph has been dogged by controversy since its invention in the early 20th century, with most scientists agreeing it is nothing more than an interrogation technique subject to the biases of the examiner. Park Jeong-kyo, a court-appointed lawyer in Jeonju, North Jeolla, agrees. He recently wrote, “Investigative agencies use the untrustworthy lie detector tests in order to pressure criminal suspects,” in an article in a newspaper published by the Korean Bar Association.
“Although many defendants ? thinking they’re innocent ? trust a lie detector and easily respond to the request to take a test, it’s very hard to pass,” he commented. “If the result of the test turns out to be a ‘lie,’ most suspects will be indicted despite their claims of innocence.”
The Public Prosecutors’ Office wrote a rebuttal in the next edition of the same newspaper. “A lie detector is measured to be 92-percent accurate according to an academy in the United States,” wrote Ji Hyung-gi, director of the Psychological Analysis Department of the Supreme Public Prosecutors’ Office. “It also acts to prove one’s innocence,” he added. “The test results and the courts’ verdict matched around 81.3 percent of the time, and the court recently started to take notice of past research and results.”
Park then published a second challenge. “The investigative agency may take pride in a lie detector’s accuracy of over 90 percent,” he wrote. However, even if one were to grant the accuracy of that percentage, he argued, “the other 10 percent can produce a guilty verdict for an innocent defendant.
“I’ve seen many test results that showed both plaintiffs and defendants were lying.
In a phone interview, Park elaborated on his crusade. “I wanted to illustrate habitual practices done by some government agencies that utilized incorrect test results in order to induce a false confession. If the defendant rejects a request to take a test, [prosecutors] should not record the rejection as if it implies guilt.”
Ji at the prosecutors’ office responded, “We are prepared to prove how scientific and rational a lie detector test is to not only lawyers but also to the media.”
The Supreme Court of South Korea has not fully recognized the admissibility of lie detector tests. One ruling in a hit-and-run trial in May 2005 said, “A lie detector test lacks accurate measurability, rational questions or methods and objective interpretation ability,” acquitting the defendent. Academics also have concerns.
“If the public aversion to the concept of a machine judging a human being disappears, its results would be admitted in court,” said Lee Wung-hyuk, a professor at the Korea National Police University. He said a lie detector test is the second only to genetic evidence in its accuracy.
Still, Lee Duk-hwan, professor of chemistray at Sogang University and a member of the advisory committee on police equipment at the National Police Agency, said, “The physiological changes detected by the test depend not only on lies but also on personality or testimony. Technology at the present time cannot perfectly distinguish such differences.”
By Choe Sun-uk [[email protected]]
with the Korea JoongAng Daily
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