In response to petitioning by civic groups, the Control Yuan has agreed to review polygraph testing — commonly known as a lie detector test — which is often taken as proof of guilt in criminal judgements. This news highlights the suspicion that polygraphs, which the judiciary regards as highly dependable, might be pseudoscience.
The precondition for the test to be effective is whether lying can cause specific physiological reactions that are beyond a person’s control, and that these reactions can be measured using special equipment and the results interpreted by experts. However, while this premise may seem scientific, it has always been in doubt.
Those who question the effectiveness of polygraph testing do so because they doubt its objectivity. Questions of particular concern are whether the examiner has sufficient expertise, whether the equipment used is working effectively, whether the testing environment is normal and so on. All these factors can influence the outcome of the test. Furthermore, given that each person is physiologically different, how can there be consistent criteria for judgement? By comparison, other forensic techniques, such as DNA profiling, do not involve the aforementioned variables, and are more accurate and can be verified by other experts. Relatively speaking, polygraph tests are subject to many forms of interference and lack a feature that is very important in science: replicability. This means that results cannot be checked for accuracy because it cannot be repeated and this is the Achilles heel of lie detection tests.
Although the criminal justice system does not exclude polygraph testing as evidence, it does require examiners to have expert training and experience. It requires the instruments used to be of good quality and functioning normally. For a polygraph test to be accepted, the test environment must be free of interference and it can only be done when the examinee is in a normal physical and mental state and fully conscious.
To ensure that examinees are in the required state, examiners should tell them that they have the right to refuse testing and inform them about the possible effects and consequences of the test. Test subjects should first be medically examined to ensure they are in a fit mental and physical state to be tested. The fact that there are so many requirements exposes the concern that lie detector tests carried out under duress violate a suspect’s right to defense, and that the results are likely to be distorted.
Although judicial practice has strict requirements around polygraph results, in reality, these requirements may not be sufficient, because when the test environment is controlled by the interrogator and the examinee is in a state of isolation, it is doubtful whether the examinee can be in a normal physical and mental state even if they are innocent. Furthermore, lie detector tests are usually done when prosecutors think the accused is not telling the truth. Examiners might be prejudiced and it is hard to be sure that they are truly objective. Even if a suspect does not confess, these factors will make it hard not to fail the test. Such results are therefore a quasi-confession, which seriously violates a person’s right to non-self-incrimination.
In 1997 a soldier named Chiang Kuo-ching (江國慶) was executed after being wrongfully convicted of killing a five-year-old girl. Not only was he forced to confess under torture, but investigators treated his failure of a lie detector test as iron-clad proof of his guilt. This false result, plus a lot of other bogus evidence, meant an innocent man was executed. This is precisely why all so-called scientific forms of evidence, including polygraphs, need to be re-examined.
Wu Ching-chin is chair of Aletheia University’s Department of Law.
Translated by Julian Clegg
Minister of Labor Hung Sun-han (洪申翰) on April 9 said that the first group of Indian workers could arrive as early as this year as part of a memorandum of understanding (MOU) between the Taipei Economic and Cultural Center in India and the India Taipei Association. Signed in February 2024, the MOU stipulates that Taipei would decide the number of migrant workers and which industries would employ them, while New Delhi would manage recruitment and training. Employment would be governed by the laws of both countries. Months after its signing, the two sides agreed that 1,000 migrant workers from India would
On March 31, the South Korean Ministry of Foreign Affairs released declassified diplomatic records from 1995 that drew wide domestic media attention. One revelation stood out: North Korea had once raised the possibility of diplomatic relations with Taiwan. In a meeting with visiting Chinese officials in May 1995, as then-Chinese president Jiang Zemin (江澤民) prepared for a visit to South Korea, North Korean officials objected to Beijing’s growing ties with Seoul and raised Taiwan directly. According to the newly released records, North Korean officials asked why Pyongyang should refrain from developing relations with Taiwan while China and South Korea were expanding high-level
Japan’s imminent easing of arms export rules has sparked strong interest from Warsaw to Manila, Reuters reporting found, as US President Donald Trump wavers on security commitments to allies, and the wars in Iran and Ukraine strain US weapons supplies. Japanese Prime Minister Sanae Takaichi’s ruling party approved the changes this week as she tries to invigorate the pacifist country’s military industrial base. Her government would formally adopt the new rules as soon as this month, three Japanese government officials told Reuters. Despite largely isolating itself from global arms markets since World War II, Japan spends enough on its own
When 17,000 troops from the US, the Philippines, Australia, Japan, Canada, France and New Zealand spread across the Philippine archipelago for the Balikatan military exercise, running from tomorrow through May 8, the official language would be about interoperability, readiness and regional peace. However, the strategic subtext is becoming harder to ignore: The exercises are increasingly about the military geography around Taiwan. Balikatan has always carried political weight. This year, however, the exercise looks different in ways that matter not only to Manila and Washington, but also to Taipei. What began in 2023 as a shift toward a more serious deterrence posture
RSS