House prosecutors have included a psychiatrist and former Davao City court sheriff Abe Andres among their witnesses in the upcoming impeachment trial of Vice President Sara Duterte.

The two witnesses are expected to support the Article of Impeachment concerning Duterte's alleged verbal threats against high-ranking government officials.

In an online interview with reporters on Friday, 26 June, Lanao del Sur Rep. Zia Alonto Adiong said the psychiatrist was included to provide an objective, professional assessment of the Vice President's public statements, free from political bias.

Adiong said the psychiatrist's testimony would help determine whether the defense's assertion that Duterte's remarks were not serious is supported by expert evaluation.

"The psychiatrist would be objective in trying to respond to the questions of both the defense and the prosecution," he said.

"The only way for the public to know that these threats were made seriously, with clarity and intent, is for an expert to observe and assess the utterances of threats against the President, the First Lady, and the former Speaker," he added.

Adiong said the psychiatrist's testimony would help both the impeachment court and the public determine whether the alleged threats were intentional and properly understood within their context.

The prosecution also intends to present evidence that it says demonstrates a pattern of violent behavior by Duterte, which prompted the inclusion of Andres as a witness.

Although the incident involving Andres occurred before Duterte's current term as vice president, House prosecution spokesperson Atty. Benjamin Tolosa said the rules allow the presentation of evidence to establish a person's behavioral pattern.

"Under the rules, it is allowed to present evidence to establish a behavioral pattern, to establish the propensity of a person to resort to violence, for example," Tolosa said.

He declined to elaborate further on Andres' expected testimony.

Andres was punched several times by Duterte during a demolition operation in Davao City in 2011 when she was serving as mayor.

Adiong argued that the incident reflected a pattern of conduct that could amount to a betrayal of public trust, stressing that no public official is above the ethical standards required by law.

"It also speaks about the attitude ... the impunity, the culture of impunity that we would try to address," he said.

With the pretrial conference concluded, the impeachment trial before the Senate is scheduled to begin on 6 July.

Tolosa said the prosecution expects to present its first witness on the opening day of the trial.