MANILA—Davao City Mayor Sara Duterte on Thursday posted a photo of a "triad tattoo" after Senator Antonio Trillanes asked her sibling Davao City Vice Mayor Paolo Duterte to show his back tattoo at a public hearing.

"Trillanes and USDea. Paki Decode. Please. 😝😝😝 By the way, thank you Edwin Miraflores for the triad tattoo," the mayor captioned her Facebook post.

Trillanes earlier asked the President's son to show his back tattoo as this would purportedly prove that he is part of the triad, an international crime syndicate.

Paolo's lawyer Rainier Madrid said he advised Duterte to decline Trillanes' request as the body mark was not related to the subject of the nearly 4-hour hearing.

"We do not want to dignify Trillanes' accusations and fishing expedition. The issue discussed in the committee is not [the] existence of the tattoo," he said.

Customs fixer Mark Taguba in a previous hearing alleged the young Duterte and his brother-in-law, Manases Carpio, were part of the "Davao Group" that allegedly facilitated smuggling in the Bureau of Customs.

A day after his testimony, he released a statement to the media clearing both Duterte and Carpio.