MANILA – Investigators may ask Ricardo Hernandez, the driver of former Department of Public Works and Highways (DPWH) Undersecretary Ma. Catalina “Cathy” Cabral, to undergo a polygraph test, the National Bureau of Investigation (NBI) said.

NBI spokesperson Attorney Palmer Mallari clarified that a polygraph is only an investigative tool and is not admissible as evidence. It will be requested only if deemed necessary.

“In the event that the investigators are not yet convinced on the statements being offered by a witness, malamang pwedeng maipatawag para may request for polygraph examination,” Mallari said.

He added, “Pero kung halimbawa naman ang mga imbestigador ay kumbinsido na sa mga nakita nilang ebidensya at ito’y nagtutugma doon sa statements na ino-offer naman ng particular na witness, malamang wala nang need for a polygraph examination. It’s actually a hypothetical statement.”

Mallari said Hernandez is not under NBI custody.

The driver earlier told authorities that he and Cabral were traveling along Kennon Road toward La Union when she asked him to stop and leave her there. Hernandez then went to a nearby gasoline station and later returned to the area around 5 p.m. but did not see Cabral. He subsequently returned to the hotel where Cabral was staying, but she was not there. He reported the incident to the police at around 7 p.m.

Cabral was later found unconscious and unresponsive along the side of Bued River, at least 20 meters below the highway.

The NBI said it prefers to finish its investigation before commenting on findings by the Department of Interior and Local Government and the Philippine National Police, which suggested “no foul play” in Cabral’s death.