Published 18 March 2022, The Daily Tribune

The case of Herrera vs Alba (G.R. 148220, 15 June 2005) looked back on the history of citation, use, and accordance of the probative value of DNA evidence in various cases in jurisprudence in seeking to answer questions on the probative value of DNA testing in paternity and filiation suits. Note that it was decided prior to A.M. 06-11-5-SC or the Rule on DNA Evidence promulgated by the Supreme Court only on 2 October 2007.

To illustrate, in the 2002 case of People v. Vallejo [431 Phil. 798 (2002)], the Supreme Court affirmed the accused’s conviction of rape with homicide and sentenced him to death on the basis of DNA profile from the vaginal swabs taken from the rape victim which matched the accused’s DNA profile. The Court conceded that Vallejo discussed the probative value, not admissibility, of DNA evidence. It observed that, by 2002, there was no longer any question on the validity of the use of DNA analysis as evidence.

Going deeper into the probative value of DNA analysis as evidence, the Supreme Court had cautioned trial courts to be cautious in giving credence to such as evidence. This refutable presumption of paternity should be subjected to the standards that, in assessing the probative value of DNA evidence, courts should consider:

— how the samples were collected,

— how they were handled,

— the possibility of contamination of the samples,

— the procedure followed in analyzing the samples, whether the proper standards and procedures were followed in conducting the tests, and the qualification of the analyst who conducted the tests.

These standards would later be modified in accordance with acceptable standards in accordance with advancements in technology and codified in the Supreme Court’s Rule on DNA Evidence.

The Supreme Court further ruled that in a paternity test, if the man’s DNA types do not match that of the child, the man is excluded as the father. But if the DNA types match, then he is not excluded as the father. In other words, a complete match between the DNA profile of the child and the DNA profile of the putative father does not necessarily establish paternity. Hence, following the highest standard adopted in American jurisdiction, trial courts should require at least 99.9 percent as a minimum value of the Probability of Paternity or “W” prior to a paternity inclusion.

DNA analysis that excludes the putative father from paternity should be conclusive proof of non-paternity if the value of W is less than 99.9 percent DNA analysis that excludes the putative father from paternity should be conclusive proof of non-paternity. If the value of W is less than 99.9 percent, the results of the DNA analysis should be considered as corroborative evidence. If the value of W is 99.9 percent or higher, then there is the refutable presumption of paternity.

It must be noted that these rules were carried over to the Rule on DNA Evidence in regard to evaluating the results of DNA testing.

Lastly, the Supreme Court ruled that obtaining samples from petitioner for DNA testing does not violate his right against self-incrimination. Section 17, Article 3 of the 1987 Constitution provides that “no person shall be compelled to be a witness against himself.” It is well settled that the privilege is applicable only to testimonial evidence. Time and again, the Supreme Court has ruled that the right against self-incrimination is limited to a prohibition on the use of physical or moral compulsion to extort communication or testimonial evidence from a defendant and not an exclusion of evidence taken from his body when it may be material.

In Part 3 of our series, we will further discuss DNA testing in light of the Rule on DNA Testing promulgated in 2007. (To be continued)

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