Polygraphs' admissibility in Philippine courts: A Complete Guide

If you were to go back in time to the 1930s and 1940s in the Philippines, you would find that the use of lie detection techniques was not uncommon in criminal investigations. During that time, police investigators would use crude methods such as thumb printing, handwriting analysis, and physical torture to extract confessions from suspects. However, the accuracy of these methods was often questionable, and the use of physical coercion was not ethical.

It wasn’t until the 1960s that polygraph testing was first introduced in the Philippines. The Philippine National Police (PNP) was the first law enforcement agency to use the polygraph in criminal investigations. However, it was only used sporadically and on a case-by-case basis.

A vintage black-and-white image of a lady taking the polygraph exam

In the 1990s, the use of polygraph testing gained more attention in the Philippines due to high-profile criminal cases that were solved through the use of this technology. One of the most notable cases was the investigation of the Philippine National Bank robbery in 1991, where the PNP used a polygraph test to identify the suspects. Since then, the use of polygraph testing in the Philippines has become more common. For example, the Philippine National Police (PNP) uses polygraph testing in their pre-employment screening of new recruits, while the National Bureau of Investigation (NBI) conducts polygraph testing as part of their background investigation for security clearance. However, the admissibility of polygraph results as evidence in court remains a controversial topic.

The purpose of this article is to provide you with a clear and informative overview of the admissibility of polygraph tests in Philippine courts. You will learn about the legal framework for the admissibility of evidence, the current status of polygraph tests in the Philippines, and a better understanding of the role of polygraph tests in criminal cases.


Overview of the Philippine legal system

At the core of the Philippine legal system is the Philippine Constitution, which serves as the highest law of the land. The Constitution outlines the powers and functions of the government and guarantees certain rights and freedoms to the people.

The Philippine legal system is composed of several branches, including the executive, legislative, and judicial branches. The executive branch is headed by the President and is responsible for implementing laws and policies. The legislative branch is composed of the Senate and the House of Representatives, which are responsible for creating and passing laws. The judicial branch is headed by the Supreme Court and is responsible for interpreting and enforcing laws.

In the Philippines, criminal cases are heard by either the Regional Trial Court or the Municipal Trial Court, depending on the severity of the offense. The Regional Trial Court has jurisdiction over major criminal cases, while the Municipal Trial Court has jurisdiction over minor offenses, such as traffic violations.

In criminal cases, the accused is presumed innocent until proven guilty beyond a reasonable doubt. The prosecution has the burden of proving the guilt of the accused, and the accused has the right to remain silent and to be represented by legal counsel.

The Philippine legal system recognizes the principle of due process, which ensures that every individual is entitled to fair and impartial treatment under the law. This means that criminal investigations and court proceedings must be conducted in accordance with the law and in a manner that protects the rights of both the accused and the victim.


Legal basis for the use of polygraph in the Philippines

Female lie detector examinee dressed in black

In the Philippines, the use of polygraph tests as evidence in court is not explicitly prohibited by law. However, the legal basis for their admissibility is not clear-cut, and the courts have not consistently ruled on the matter.

There are several legal principles and precedents that may influence whether or not a court will allow the introduction of polygraph evidence.

One such principle is the requirement that evidence presented in court be relevant and material to the case. This means that the evidence must have a direct bearing on the issues at hand and must be capable of influencing the court’s decision. Polygraph evidence may be deemed irrelevant or immaterial if it is not sufficiently probative of the facts in dispute.

Another principle is the requirement that evidence presented in court be reliable and trustworthy. The reliability of polygraph evidence is a matter of debate, as there is no consensus among experts as to the accuracy and validity of the tests. Courts may also be wary of admitting polygraph evidence because of the potential for manipulation and human error.

The admissibility of evidence is determined by the trial judge, who has the discretion to exclude evidence that is immaterial, irrelevant, or obtained illegally.


Philippine laws and regulations on the use of polygraph testing

Philippine laws and regulations on the use of polygraph testing have been established to regulate the use of such tests in various industries and to protect individuals from the misuse of these tests:

The Philippine Constitution: The Philippine Constitution guarantees the right to due process and the presumption of innocence until proven guilty. This means that any evidence that is obtained illegally or through means that violate these rights cannot be used in court. The admissibility of polygraph testing as evidence in court is still a contentious issue.

Philippine National Police Manual on Polygraph: The Philippine National Police (PNP) has a manual on the use of polygraph testing in criminal investigations. The manual provides guidelines on how to conduct polygraph tests and emphasizes the importance of adhering to the law when using this tool. The PNP also requires that any polygraph examiner be certified by a recognized polygraph association and undergo regular training and re-certification.

The Data Privacy Act of 2012: This law requires that any data gathered through polygraph testing be collected and processed in a lawful and fair manner and that individuals be informed of the purpose of the test and their rights regarding the data collected.

In addition to the Data Privacy Act, there are also specific regulations that govern the use of polygraph testing in various industries. For example, the Civil Aviation Authority of the Philippines requires pilots and air traffic controllers to undergo polygraph testing as part of their pre-employment screening process. However, these tests can only be conducted by licensed examiners and must be voluntary.


Admissibility of polygraph evidence in the Philippines

A hand pointing to a lie detector graph on a computer screen

In 1991, the Philippine Supreme Court issued a landmark decision in the case of People v. Teehankee Jr. In this case, the Court held that the results of a polygraph test are inadmissible as evidence in court. The Court noted that polygraph tests have not yet gained scientific acceptance as a reliable means of determining the truth or falsity of statements. The Court also observed that the reliability of polygraph tests is highly dependent on the skill and expertise of the examiner.

Despite the strict stance of the Philippine Supreme Court, there have been instances where polygraph evidence has been considered in court. In some cases, the court has allowed the admission of polygraph evidence as corroborative evidence, provided that it is not the sole basis for a conviction. In these instances, the Court has emphasized that the polygraph evidence must be accompanied by other evidence that is sufficient to establish guilt beyond a reasonable doubt.


Exceptions to the Rules of Court for Polygraph Evidence

Despite the fact that the Supreme Court has ruled that polygraph testimony is typically not admissible in court, there are some exceptions to this rule:

  1. One exception is when both parties agree to the admissibility of polygraph evidence. In such a case, the parties must enter into a written stipulation or agreement that the polygraph results may be presented as evidence in court. The stipulation must also state the specific questions asked during the polygraph test and the answers given by the examinee.
  2. Another exception is when the polygraph evidence is used to impeach the credibility of a witness. This means that the results of a polygraph test may be used to challenge the truthfulness of a witness’s testimony, but not as evidence of the truth of a particular fact.


Factors considered by courts in determining the admissibility of polygraph results in court

Side image of a young female polygraph examinee dressed in black.

When courts in the Philippines consider the admissibility of polygraph results as evidence, they typically examine a number of factors to determine whether or not to admit such evidence. One key factor is the reliability of the polygraph test and the qualifications of the person administering it. The court will also consider whether the test was conducted in a manner that was fair to the accused or the witness and whether any relevant procedural requirements were followed.

Another factor that courts consider is the relevance of the polygraph results to the case at hand. The court will evaluate whether the results are probative of any material fact and whether they are likely to assist the trier of fact in determining the truth of the matter at issue. If the court finds that the polygraph results are not sufficiently relevant to the case, they may not be admitted as evidence.

The courts will also examine the potential prejudice that the introduction of polygraph evidence may cause to the parties involved. This includes evaluating the potential for the polygraph results to inflame the emotions of the jury or unfairly prejudice the defendant. If the court finds that the introduction of polygraph evidence would be unfairly prejudicial, they may exclude it from the trial.

Finally, the court will consider any applicable laws, regulations, or judicial precedents on the admissibility of polygraph evidence. As discussed in previous sections, the Philippine legal system has specific rules regarding the use of polygraph evidence, and courts are bound by these rules when considering the admissibility of such evidence.


Ethical considerations

The Professional Regulation Commission (PRC) has established a code of ethics for polygraph examiners that emphasizes the importance of informed consent, confidentiality, and impartiality. Polygraph testing can have significant implications for the individuals involved, and therefore, it is important to ensure that ethical standards are upheld throughout the process.

One of the primary ethical concerns with polygraph testing is the issue of informed consent. Individuals must be fully informed about the purpose and implications of the test. They should also be informed of their right to refuse to take the test.

Another ethical consideration is the potential for the test to be inaccurate or unreliable. as the findings can be influenced by stress, anxiety, or medical conditions, and a false result might result in a wrongful conviction. Polygraph tests can produce false positives and false negatives, which can have serious consequences for the individuals being tested. Therefore, it is important to ensure that the test is administered by a qualified and experienced examiner who follows recognized protocols and procedures.

Confidentiality is another ethical concern with polygraph testing. Individuals who take the test should be assured that their results will be kept confidential and that they will only be disclosed to authorized individuals, such as law enforcement or legal professionals.

Finally, it is essential to consider the potential for bias and discrimination (such as race, gender, and socioeconomic status) in the administration and interpretation of polygraph tests. and to ensure that the test is administered in a fair and unbiased manner.



In conclusion, the admissibility of polygraph evidence in court in the Philippines is a complex issue with no clear-cut answer. Philippine jurisprudence on this matter is still developing and subject to interpretation. However, there are several factors that courts consider in determining the admissibility of polygraph results in court, such as the qualifications of the examiner, the voluntary nature of the test, and the reliability and relevance of the results.

Ethical considerations are also important when it comes to the use of polygraph testing. Test results can be influenced by a variety of factors, including the subject’s physical and mental state and the examiner’s own biases and interpretations.

Overall, it is important for courts to approach the admissibility of polygraph evidence in a thoughtful and nuanced manner, taking into account both the benefits and limitations of polygraphs.

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