Extracting DNA from bone better than blood samples —forensic analyst

A forensic analyst on Tuesday said extracting DNA from the kneecap bone of the boy riddled with stab wounds believed to be Reynaldo "Kulot" de Guzman in Gapan, Nueva Ecija last week would have yielded more accurate results compared to blood samples.

"Hindi ko alam kung tama ba na dugo yung nakuha nila. Maybe they could have tried something else, [sa] buto," Dr. Raquel Fortun told Unang Balita. "Kung sa akin yan I would try bone, pinakamadaling kunin and so far maganda ang feedback ng yield ng DNA lab [sa] patella, yung tuhod."

Fortun also wanted to know if the Philippine National Police, aside from DNA testing, also performed other tests such as dental charting, fingerprint examination, and other examinations of the physical features of the boy's body.

"Kung sa akin yan, eeksaminin ko talagang in detail lahat ng physical features. And on top of DNA testing, meron bang gumawa ng dental charting ng bangkay? May nag-attempt ba na mag-fingerprint examination? On top of that, sige kuha ka ng DNA sample pa," she said.

On Monday, PNP Deputy Director General Fernando Mendez said the buccal swabs taken from the parents of De Guzman, the boy last seen alive with 19-year-old slain student Carl Angelo Arnaiz, did not match the DNA from the body found at the creek in Nueva Ecija.

Chief Inspector Lorna Santos, chief of the PNP Crime Lab DNA division, added that the accuracy of the test they conducted was 99.9 percent.

De Guzman's parents are intending to retake the DNA tests, saying the physical features of the boy matches that of their 14-year-old son.

Fortun urged De Guzman's family and other forensic laboratories to have DNA extracted from the boy's body as soon as possible, before its scheduled burial on Wednesday.

"Buti na lang hindi pa nailibing... As long as the body is still available, e di mag-retest ka ulit. Pero sa akin, ano yan e, mina-maximize mo kung ano yung available pa, kung nandyan pa yung katawan make the most of it hindi ka lang magfo-focus on DNA," Fortun said.

She, likewise, recommended the DNA Analysis Laboratory of the University of the Philippines-Diliman to conduct the identification tests on the body.

Identification methods

Meanwhile, Fortun said DNA testing was one of the four methods to positively identify a cadaver. The three other procedures are dental charting, "dentition," and through fingerprints.

Fortun said identifying the body through a wart on his left knee and a scar on his neck is not the proper way of identifying if the cadaver belonged to De Guzman.

"Hindi positive 'yan, hindi yan nahahanay sa procedures na magbibigay ng positive identification. Napaka-subjective niyan e," she said.

The forensic analyst added that extracting DNA from the living is usually easier than extracting DNA from a cadaver since the latter might have already been contaminated.

"Madali yung doon sa living e kasi maganda yung sample mo, ang dami mo puwedeng kunin. Pero ang usual na nahihirapan sila ay dun sa bangkay, kasi nga puwedeng ma-degrade yung DNA o baka yung material kakaunti," Fortun said. — Joseph Tristan Roxas/MDM, GMA News