A Hawaii doctor who is accused of trying to murder his wife on a Hawaii hiking trail last year faced a grilling from the prosecution on his second day on the stand Thursday, after denying that he tried to kill her and testifying that he was trying to defend himself.

Dr. Gerhardt Konig, 47, is accused of beating his wife, Arielle Konig, with a rock on the Pali Puka Trail on Oahu on March 24, 2025. The anesthesiologist has pleaded not guilty to second-degree attempted murder.

His wife testified last week in the Honolulu trial that the two had traveled to Oahu from their home in Maui to celebrate her birthday. She said the couple, who have two young sons together, had been working on repairing their marriage after her husband found what she characterized as “flirty” WhatsApp messages between her and a colleague in December 2024 in what was an “emotional affair.”

Wife testifies during trial of doctor accused of trying to kill her on Hawaii hiking trail

During the cross-examination on Thursday, the prosecutor asked Gerhardt Konig how, after becoming suspicious of his wife’s phone activity, he went into “detective mode” and uncovered her messages with her coworker by monitoring her WhatsApp account.

“You’re mad, right?” prosecutor Joel Garner asked him, referring to the time he first confronted his wife about the messages.

“I was not mad,” Gerhardt Konig responded.

“You were not mad when you confronted your wife about these messages?” Garner asked.

“I was upset,” the defendant responded.

Garner also asked about the couple’s relationship after the “emotional affair” came to light — with Gerhardt Konig testifying he wanted his wife to quit her job and give up her privacy, but she was unwilling to do those things.

Parts of the cross-examination also focused on the couple’s finances and Gerhardt Konig’s prior divorce, with Garner showing the court financial and divorce documents that had been accessed on the defendant’s desktop in the weeks and months prior to the hike.

“You’re researching these financial documents and these divorce documents because you want to see how much damage you’re going to suffer in a divorce, isn’t that right?” Garner asked.

“That’s not right,” Gerhardt Konig replied.

Garner pressed Gerhardt Konig on taking his wife on such a difficult hike on her birthday. The defendant testified that when she didn’t want to continue on the narrow trail, he went on by himself and came back to find her still on the mountain.

“It was a surprise, because you still had a chance to go through with your plan to push Arielle. Isn’t that right?” Garner asked.

“That’s not right at all,” Gerhardt Konig responded.

While testifying on Wednesday, Gerhardt Konig offered a far different account of what happened on the hike than what his wife testified occurred.

Arielle Konig testified that during the hike, her husband pushed her toward the edge of the cliff and, as they wrestled on the ground, produced a syringe and vial. She said he proceeded to beat her with a rock as many as 10 times, leaving her head and face bloodied, and that she believed he was trying to knock her unconscious to drag her over the edge.

Gerhardt Konig testified that his wife pushed him first after they got into an argument about the affair.

“I felt, like, a shove, and I was almost pushed over the edge,” he said.

Opening statements delivered in trial of doctor accused of trying to kill wife on Hawaii hiking trail

Gerhardt Konig testified that they then struggled on the ground and she hit him with a rock first. He said he then took the rock from her and struck her with it twice.

He denied having any syringes or trying to pull her toward the edge of the cliff, and said he never planned on hurting her that day. After bystanders came to Arielle Konig’s aid, Gerhardt Konig left the scene.

In the aftermath, he said he felt suicidal.

“I just felt hopeless at that point in terms of everything,” he said. “I felt horrified about what I did to her, that I had caused this to her, that I had resorted to violence against my wife, the person who I love the most in the world. And I just kind of felt hopeless in terms of our relationship, too.”

Shortly after the incident, he said he made a FaceTime call to his 20-year-old son from his prior marriage, Emile Konig, in that moment to say goodbye.

His son testified about the FaceTime call on Tuesday. Asked by the prosecutor to recount what his father said during the call, Emile Konig responded, “That he would not be making it back to Maui and to take good care of the younger kids, and that Ari, my stepmom, had been cheating on him, and that he tried to kill her.”

“During that call, the next plan that he said was to jump off the cliff,” Emile Konig testified, adding that his father said he was “at the end of his rope.”

Gerhardt Konig pushed back against his son’s testimony and denied making any confession. He told the court that what he said during the call was, “She said I tried to kill her.”

Hawaii doctor accused of trying to kill wife on hiking trail pleads not guilty

Two women came upon the couple during the incident, with one telling a 911 operator, “Someone’s currently being attacked on the top of Pali Puka. There’s a man trying to kill her,” according to audio of the call played in court.

Gerhardt Konig was arrested following an hourslong manhunt, prosecutors said.

Arielle Konig testified she was treated at a hospital for “severe complex scalp lacerations” and showed the court scarring on her scalp.

Arielle Konig filed for divorce in May 2025, seeking full custody of the couple’s two children.

Gerhardt Konig, who worked as an anesthesiologist on Maui, has been in jail since his arrest. Following his arrest, Maui Health said his medical staff privileges at Maui Memorial Medical Center have been suspended pending investigation.