When local tutor Alice Ku went to Taiwan with her husband in November 2019, she fully expected to return to her job working with students in Palo Alto, Mountain View, Sunnyvale and Cupertino.

But Ku, of Mountain View and formerly of Palo Alto, vanished without a trace. To date, no one — her family, employer, students or husband — has heard from Ku, despite their numerous attempts to contact her by phone, email and SMS text. Her cellphone and laptop use and financial transactions have all ceased.

Police in Taiwan, Republic of China, say Ku, then 36, was murdered, but they have not found her body, a murder weapon or traces of what happened to her.

They say they have other evidence, based largely on cyber data and her husband's inconsistent statements. Taiwanese authorities have issued an arrest warrant for her husband, Harald Herchen, a prominent Silicon Valley inventor who owns multiple patents.

But Taiwanese officials can't extradite him because the U.S. doesn't have formal diplomatic relations with the country, and therefore has no extradition treaty, a predicament that Ku's family attorney, Andrew Watters, said must change.

Herchen remains free and lives in Los Altos, according to court documents filed in a civil lawsuit for wrongful death her family has filed against him.

He allegedly told Ku's brother that he spent a substantial sum of money trying to find her, according to an email he reportedly sent to the brother, George Ku. But under oath during a deposition, he admitted he hadn't looked for her at all, Watters said in a court declaration.

Ku's family, meanwhile, offered $1 million Taiwan dollars as reward for any news on Ku, to no avail. Her disappearance was reported by major news channels in Taiwan.

With no other recourse, Ku's parents and her brother filed a wrongful death lawsuit against Herchen in Santa Clara County Superior Court on Jan. 12, 2021. Herchen's attorney, Louis F. Doyle, maintains there's no evidence that Herchen was involved in Ku's disappearance.

Ku's trip to Taiwan to see her parents

The story of Ku's disappearance began on Nov. 23, 2019, when she and Herchen flew to Taiwan for a business trip of his. Photographs show nothing out of the ordinary: the couple standing against the backdrop of verdant mountains and a waterfall; Ku at a botanical garden; Ku posing along a walkway that wends through towering canyon walls.

A self-portrait of Ku captured her applying mascara before a mirror in the hotel bathroom. It is the last known photograph of Ku, and it was taken on the morning of her disappearance.

Ku was to take a train from the city of Hualien that morning, Nov. 29, to visit her parents at their home in Yangmei, near Taipei. Herchen said in his deposition that he dropped her off at the train station.

Herchen claimed that the last time he heard from Ku was when she sent him an email on Nov. 30. In the email, of which this news organization obtained a copy, Ku noted that Herchen would be going to his sister's wedding. The couple had planned to leave Taiwan on Dec. 1, but Ku asked him to postpone her return until Dec. 7. He responded that he would change the date for Ku's flight and would meet her in the airport lounge when he returned to Taiwan between 9:30 a.m. and 10 a.m. "like last time."

Herchen changed Ku's reservation on Dec. 1 and departed Taiwan, a police investigation showed.

He flew back to meet her on Dec. 7, but she never contacted him. He returned home on Dec. 8, he said during a Dec. 18, 2019, interview with Watters.

But Ku's parents, Weichiao Ku and Pi Lien Kuo, say they didn't know their daughter was coming; they didn't even know she was married, George Ku stated in his Dec. 22, 2022 court declaration.

Ku never arrived at her parents' home. The family didn't learn that Ku had disappeared until early in December 2019, George Ku said. The parent of one of Ku's students contacted one of her sisters, Grace, to report that Ku had missed several tutoring sessions, which had never happened in the several years that they had known Ku.

On Dec. 9, 2019, after being unable to reach his sister, George Ku and another sister filed a missing persons report with the Sunnyvale Department of Public Safety, the city in which they thought she lived. They learned that Ku had not lived at her Sunnyvale apartment for six months.

Watters tracked Ku's address to an apartment on Wright Avenue in Mountain View. On Dec. 12, 2019, George Ku and Watters went to the apartment looking for his sister. A sign on the door read "Welcome Home, Alice. I love you," but the apartment building manager said she hadn't been there for some days.

George Ku and Watters learned from neighbors that his sister lived at the apartment with an older man, identified as Harald Herchen, a German-born, Canadian citizen who was 62 at the time, 23 years older than his sister. Herchen mostly lived at a home in Palo Alto, the neighbors said. It was the first time the family had heard of the marriage, George Ku said.

Herchen, when contacted by George Ku, said that his wife often accompanied him on business trips and would stay a few extra days. Ku was looking into tours during the Taiwan trip, and he claimed that she had also contacted him by email and had a SIM card allowing her to make local telephone calls. She also had used one of his credit cards, Herchen said.

A different story

Watters, who works out of San Mateo, and San Jose attorney Todd Davis, were hired by George Ku to initially to handle conservatorship of Ku's estate, but they have uncovered multiple alleged factual inconsistencies in Herchen's story leading them to believe that Ku was murdered and that he was involved in her death.

Watters and George Ku interviewed neighbors who said that Ku and Herchen often fought — loudly — about money and that she had threatened to end the marriage. They also reportedly argued about a pregnancy.

The couple met through an online escort service, which Herchen said in a deposition that he used for sex. Their relationship had overlapped with Herchen's then-marriage to his second wife, Melissa Yu.

She died from cardiac arrest due to obstructive sleep apnea in June 2017, according to a Santa Clara County Medical Examiner report. The medical examiner noted multiple bruises on Yu's body but didn't conclude what their cause was.

George Ku said their parents never had plans to see their daughter in November or December 2019. His sister had not contacted them about the visit, and they didn't know she was in Taiwan. She had never been to their new home near Taipei and wasn't familiar with the area, he said.

It was also out of character for Ku to linger without her husband during these trips, despite Herchen's indication that she had done so in the past. Taiwan customs and immigration records found no evidence that Ku ever stayed behind for a few days when accompanying Herchen on business trips to the country, according to Taiwan police.

Herchen also claimed that Ku had sent him an email at 10:01 a.m. on Nov. 30 — a so-called "proof of life" email — that showed she was still alive after Herchen left her at the train station. But Watters, who has expertise in cyber-related matters, said the unique IP address connected with that email belongs to the hotel where Herchen was staying that same evening — after he claimed to have sent his wife to visit her parents.

Investigators from the Taiwan Criminal Investigation Bureau (CIB) of the Taiwan National Police Agency confirmed the IP address belongs to the hotel where Herchen testified in a deposition that he was staying in alone on Nov. 29, according to a Nov. 22, 2022, court declaration by Li Tsung Su, the Taiwan Criminal Investigation Bureau lead investigator in Alice Ku's case.

After police collected hotel check-in records, CCTV footage, cellphone communications records, email login and internet surfing records, they found that statements made by Herchen allegedly didn't match the evidence, Su said.

"It's highly believe(d) that defendant Harald Herchen was involved in homicide and in violation of Article 271 of our Criminal code," he wrote.

The Criminal Investigation Bureau is roughly the equivalent of the U.S. Federal Bureau of Investigation, Yang Chi Lee, director of international criminal affairs for the agency, said in a Nov. 22, 2022, court declaration.

"The defendant claims to have taken Alice Ku to the Hualien train station on Nov. 29, 2019. Our investigation determined that the signals for Alice's cellular telephone appear in Hualien but do not appear near the train station at that time," he said.

Ku's internet login history of her email abruptly stopped on Nov. 29, 2019, which is inconsistent with her use pattern, the detective said. Ku and her sister Josephine had exchanged text messages nearly every day in November 2019, but the messages from Ku abruptly ended, according to police investigators.

Despite Herchen's claim of receiving an email from Ku on Nov. 30, the email was actually dated Nov. 29, 2019, and the time stamp was at 3:01 p.m., according to Lee.

"We have determined, based on our investigation including the above-referenced facts, that: Alice Ku is dead and is the victim of a homicide; that Alice Ku was killed on or before November 29, 2019, and that Defendant Harald Herchen is a suspect in that homicide," he said.

Given the "critical inconsistencies" between the collected evidence and Herchen's statements, behavior and testimony under oath, the Criminal Investigation Bureau issued a warrant for Herchen's arrest for homicide on Dec. 28, 2020.

"The warrant is outstanding and the Defendant is wanted for questioning due to his involvement and his absence in Taiwan court. We continue to investigate this case through information provided by foreign law enforcement including the FBI, which has been actively assisting us and the American Institute in Taiwan (the de facto United States embassy in Taiwan)," Lee said.

Watters said in a December email to the FBI's Director Christopher Wray that the agency's field office has been unresponsive to his requests for follow-up on the case. The San Francisco Field Office did not respond to requests for comment made by this news organization nor for confirmation that it was investigating the case.

Watters said that despite Herchen's claim that Ku had used one of his credit cards, Copy Factory produced information showing that Herchen allegedly paid for an order with Ku's credit card after her disappearance.

Ku's last two phone calls the evening of Nov. 28, 2019, to tutoring clients, were from a Wi-Fi network, according to phone records.

After Ku's Nov. 29 disappearance, Herchen left a single voicemail for her on Dec. 7, but he made no other calls to her. There were no outgoing calls from Ku's phone after her disappearance, Watters said.

Watters also noted that Herchen contradicted statements he made to George Ku in an email. Herchen told George Ku on Jan. 9, 2020, that he "spent considerable sums in getting Alice to come back," but under oath he later admitted that he hadn't done anything to try to find her.

Herchen's attorney denied the allegations against his client.

"Plaintiff has no direct evidence — NONE. Plaintiff's 'key evidence' is speculation and conjecture. Harald Herchen had nothing to do with Alice's disappearance," Louis Doyle wrote in a Feb. 8 email.

Doyle sought to have the civil lawsuit dismissed, but Superior Court Judge ​​Socrates Manoukian rejected the motion and the trial could move forward, he ruled on Dec. 28, 2022.

"In this court's opinion, the evidence submitted by the parties presents a triable issue of material fact with regard to whether Decedent's disappearance is the result of (caused by) defendant Herchen's conduct. While the court would agree that speculation and conjecture is insufficient to establish defendant Herchen's liability, evidence of defendant Herchen's untruthfulness here in multiple instances creates more than just a weak issue of fact," Manoukian wrote.

The civil trial could begin in early fall.

Watters said he is driven to get justice for Alice Ku. Ku's car, a dark red Honda Civic, was still parked in its stall at the Mountain View apartment complex when Watters visited in December 2019.

"It was caked with a thick layer of dust. The windshield had a thinner layer of dust, but still thick enough that the car had not been moved in at least a couple of months. Tutoring books were visible in the back seat, and the brakes appeared rusty from lack of use," Watters said.