MANILA - Dexter Carlos, a security guard whose entire family was butchered in their home in Bulacan province, is aggrieved that policemen are now investigating him for the crime, his lawyer said Wednesday.

"Kausap ko nga po kahapon saka kanina. Malungkot, masama ang loob [niya]," Public Attorney's Office (PAO) chief Persida Rueda-Acosta told radio DZMM.

"Ang sabi niya, after 14 days, saka siya ituturo na siya ang ipo-polygraph saka siya i-investigate."

Carlos discovered the lifeless bodies of his 3 children, wife and mother-in-law when he got home from work in San Jose del Monte, Bulacan last June 27.

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A construction worker, identified as Carmelino Ibañez, has confessed to murdering the victims and raping the 2 women. He said he and 2 accomplices were drunk and high on drugs.

Ibañez however later claimed that policemen tortured and threatened him to own up to the murders. He remains in police custody.

Three "persons of interest" in the case meanwhile have been killed in separate vigilante attacks.

On Tuesday, investigators announced that they will invite Carlos to shed light on some unusual features of the crime scene, including the lack of bloodstains in certain parts of the victims' house.

"Malayo sa katotohanan na itong si Mr. Carlos ay magiging primary suspect natin... Pero papano natin masasabi na si Mr. Carlos ay walang kinalaman sa krimen kung hindi natin ma-establish ang kinaroroonan niya, anong ginagawa niya noong nangyari ang krimen," said Bulacan police chief Senior Supt. Romeo Caramat.

PAO's Acosta railed against this development, saying their own psychological assessment of Carlos did not yield any apparent motive that could tie him to the crime.

"Ako, walang ga-hiblang pagdududa sa kanya dahil isipin mo, ang motibo, na-establish na ng mga pulis sa crime scene. Nakahubo ang asawa niya at saka kanyang biyenan. Bakit naman niya gagahasain ang kanyang asawa saka iyung anak niya na isang taon, papatayin niya?

CCTV footage from a bank, she added, would show that Carlos was on guard duty on the night of the murders.

A crime watchdog meanwhile said policemen should have started their investigation with Carlos because the foremost persons of interest should be victims' relatives and close friends, as well as those who were first to discover a crime scene.

"Dapat na-provide nila iyung si Dexter, in-undergo ang psychiatric neuro test, just to guide them kung nagsasabi ng totoo. Sa police investigation po, dapat po malawak, lahat suspek," said Arsenio "Boy" Evangelista, spokesperson of the Volunteers Against Crime and Corruption.

"Tingin ko, dito ulit nagkamali ang police investigation -- na hindi nai-subject ang asawa mismo, considering na siya ang unang nakakita sa crime scene."

Evangelista added that police should review their protocol in crime investigation.