Polygraphs' admissibility in Philippine courts: A Complete Guide

Polygraph tests, commonly known as lie detector tests, have long been a controversial topic when it comes to their admissibility as evidence in legal proceedings. Also called deception detection tests, polygraphs measure and record certain physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while asking a subject a series of questions. The belief is that deceptive answers will produce physiological responses that can be detected.

In the Philippines, polygraph test results are generally inadmissible as evidence in court. However, there are certain exceptions and circumstances where they have been allowed, usually subject to certain conditions. This guide will provide an overview of polygraphs’ admissibility in Philippine courts by exploring:


What Is a Polygraph Test?

Female lie detector examinee dressed in black

Before delving into the admissibility of polygraphs, it’s important to understand what exactly a polygraph test is and what it aims to measure.

  • A polygraph device records physiological data such as blood pressure, pulse, respiration, and skin conductivity. It does this while asking the subject a series of questions, some of which are neutral/control questions and others that pertain to the issue being investigated.
  • The belief is that deceptive or false answers will produce measurable physiological reactions that can be interpreted by the polygraph examiner. However, things like anxiety can also affect these measurements.
  • Polygraph proponents believe the tests can accurately detect deception at rates above 90%, provided the examiner is properly trained. Critics argue there is insufficient scientific evidence to support their accuracy and that polygraphs can be beaten.


History of Polygraph Use in the Philippines

  • The use of polygraph testing first emerged in the Philippines in the 1960s, introduced by the National Bureau of Investigation (NBI).
  • The Metropolitan Police District (MPD) began utilizing polygraph exams in the 1970s. Other law enforcement agencies gradually followed suit.
  • By the late 1980s, polygraph tests were widely used by law enforcement in criminal investigations. They were also sometimes used by private companies for employee screening.
  • However, there was no clear legal framework for the use and admissibility of polygraphs at first. Jurisprudence developed over time to provide some guidance.


Key Jurisprudence on Polygraph Admissibility

A gavel and the Philippine flag in the background.

Several key Philippine Supreme Court decisions have helped shape the landscape regarding polygraphs in legal proceedings:

  • People v. Teehankee Jr. (1995) – This high profile murder case established that polygraph results themselves are inadmissible as evidence. However, testimony about polygraph examinations may be allowed, subject to certain conditions. This remains the prevailing rule today.
  • People v. Olivio (2014) – Reaffirmed the Teehankee ruling that polygraph results themselves cannot directly establish guilt or innocence. However, testimony concerning the taking of the test may be allowed, subject to discretion and provided there is no abuse.
  • Limbaja v. People (2017) – The Court ruled that even testimony about a polygraph examination is inadmissible if the opposing party did not have an opportunity to cross-examine the examiner. This highlights the importance of the rights of the accused.


When Polygraph Test Results and Testimony May Be Allowed

Based on key jurisprudence established by the Philippine Supreme Court, polygraphs and testimony concerning them may be permitted under the following circumstances:

  • During pre-trial investigation by prosecutors or law enforcement, results may be considered in deciding whether charges will be filed.
  • If the opposing party does not object, testimony that a polygraph test was conducted may be allowed. The results themselves cannot be revealed.
  • If both parties stipulate and agree to the admission of results. However, the Court still has discretion to exclude prejudicial evidence.
  • As evidence to impeach or corroborate the credibility of a witness. The Court has discretion over this.
  • The Court may allow testimony if the opposing party had an opportunity to cross-examine the polygraph examiner.


Requirements for Valid Polygraph Examination

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

For testimony concerning a polygraph test to be potentially admissible, certain standards must be met:

  • The polygraph equipment used must be properly functioning and calibrated.
  • The examiner must be qualified and able to produce certification or license as a polygraphist.
  • Proper procedures must be followed during the examination, including pre-test interview.
  • The subject must have voluntarily agreed to undergo the polygraph test without coercion.
  • Charts and other records related to the polygraph exam may be required as evidence.


Meeting these standards provides the best chance for polygraph-related testimony to be permitted, if the Court deems it appropriate.


Role of the Judge’s Discretion

Ultimately, the trial judge has a significant vote in deciding whether or not to allow any testimony concerning polygraphs during court proceedings.

  • He will consider whether the evidence is substantially relevant to the particular case and its probative value.
  • He will determine if the rights of the accused are upheld, including the right to cross-examine.
  • If the judge finds the polygraph evidence to be prejudicial, misleading, confusing, or wasting time, they may exclude it even if parties agree to its admission.
  • The judge may limit the scope of polygraph-related testimony allowed.


Opposition to Polygraph Admissibility

View from above of a girl doing the lie detector test

Despite some instances where testimony has been permitted, there remains strong opposition from many in the legal community regarding polygraphs in court. Arguments against their admissibility include:

  • Unproven Accuracy – There is disagreement in the scientific community regarding the reliability and accuracy rate of polygraphs. Critics argue they can be defeated with countermeasures.
  • Infringes on Rights of Accused – Polygraphs are seen by some as infringing on the rights of the accused to remain silent and not incriminate themselves. Results could put pressure to confess.
  • Prejudicial Against Accused – There are concerns that polygraph results or testimony would be overly prejudicial against defendants, outweighing probative value. Juries may give undue weight.
  • Violates Due Process – Admitting polygraph evidence is seen by some as violation of due process rights and the presumption of innocence that the accused are entitled to.


While advocates argue the tests can be useful, opposition rooted in these concerns persists in many legal circles.


Best Practices for Attorneys

For attorneys involved in cases where polygraph examinations are a factor, some best practices include:

  • Seek to cross-examine the polygraph examiner, request credentials, and scrutinize procedures.
  • Consult experts to assess the examiner’s qualifications, methods, and the validity of conclusions.
  • Challenge the validity and reliability of the specific polygraph equipment and questioning used.
  • Object to admission if you believe the prejudicial impact outweighs probative value.
  • Argue for the exclusion of direct polygraph results, and limit testimony scope.
  • Get client’s explicit consent prior to any stipulation on polygraph admissibility.



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

While polygraph results themselves remain inadmissible in Philippines courts according to prevailing jurisprudence, testimony concerning examinations may be permitted in certain circumstances and subject to judicial discretion. The qualifications of the examiner and protection of the accused’s rights are key considerations. While their accuracy remains debated, polygraphs continue to play a controversial role in Philippine legal proceedings when handled properly under strict supervision of the trial judge.


Are polygraph results admissible in Philippine courts?
Polygraph results are generally not admissible as evidence in Philippine courts. However, they may be used as a basis for further investigation or to corroborate other evidence.
Reliability of polygraph testing in the Philippines depends on several factors, such as the expertise and experience of the examiner, the quality of the equipment used, and the conditions under which the test is conducted.
The rights include the right to be informed of the purpose of the test, the right to refuse to take the test, and the right to have an attorney present during the test. The examiner must also provide a clear and accurate explanation of the questions to be asked and the procedures to be followed.
The validity is subject to debate. While some law enforcement agencies and private companies rely on them as a tool for screening potential employees or investigating criminal activity, others question the validity due to the potential for examiner bias, inaccuracies in interpretation, and variations in the physiological responses of different individuals.
There are several types of courts in the Philippines, including the Supreme Court, Court of Appeals, Regional Trial Courts, and Municipal Trial Courts. The exact number of courts can vary over time as new courts are established or existing ones are dissolved or consolidated.
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