The wife and children of the longest-held American hostage in Iran testified to the ongoing, nearly 13-year-long ordeal of Robert A. Levinson, asking a federal judge on Wednesday to impose $1.5 billion in damages on the government of Iran to deter future hostage-taking.

The opening of a two-day hearing in federal court in the District provided wrenching details about the disappearance of Levinson, a retired FBI agent who vanished in 2007 under murky circumstances in Iran while on an unauthorized mission for the CIA.

Levinson’s youngest daughter, Samantha, then 16 and now 29, said she was diagnosed with post-traumatic stress disorder and has recurring nightmares of seeing her father beheaded.

“I hit the Dad jackpot,” she testified, before reading an email Levinson sent two days before his disappearance as she was running for student office, using pet names that brought laughter and sobs from her siblings in court.

Iran last month acknowledged for the first time that it had an open court case involving Levinson, who was detained on Iran’s Kish Island on March 9, 2007. The official response to a family complaint filed in 2016 with the United Nations Working Group on Enforced or Involuntary Disappearances was the first formal indication he may be in Iran’s custody and alive since 2011, when his captors sent his family photos of him chained and dressed as a Guantanamo detainee.

“This is an American tragedy, this is a tragedy without end. . . .It is difficult to imagine the pain they have gone through,” said the family’s attorney, David L. McGee. He said Levinson, who would be 71, has been “cut off and hidden from the world.”

The lawsuit by Levinson’s wife, Christine Levinson, and their seven children seeks $150 million in compensatory and $1.35 billion in punitive damages from Iran. It alleges that he was “disappeared” by the Tehran government, or agents or proxies under its control, and subjected to torture and held incommunicado from his family, the U.S. government and the American Red Cross.

U.S. District Judge Timothy J. Kelly is hearing testimony by relatives, a business associate, a former lead FBI case agent and expert witnesses, documenting the circumstances of Levinson’s capture and detention and Iran’s actions. As in similar lawsuits brought in the United States, Iran has not appeared in court to defend itself, leaving it to a federal judge to enter a default judgment and calculate damages if he finds the nation responsible for torturing or taking Levinson hostage while Iran was a U.S.-designated state sponsor of terrorism.

The United States has rewards totaling $25 million for information leading to his return.

Levinson is one of many U.S. citizens, some of them dual nationals, who the United States contends are held on baseless grounds by Iran as it seeks the release from U.S. prisons of Iranians held mostly for convictions related to sanctions violations.

Levinson’s family noted that Iranian state-owned Press TV reported in April 2007 that he had been held by Iranian security forces since his disappearance, at age 59, with health problems. The family alleged his capture was a response to the defection to the West weeks earlier of a former general of the Iranian Revolutionary Guard Corps, Ali Reza Asgari.

In court Wednesday, the family put on evidence that Levinson’s lawyers and family were contacted by a Syrian businessman to meet in Cyprus about Levinson’s release with representatives of Hezbollah, the Iranian-backed Lebanese militia and U.S.-designated terrorism group.

Former Levinson FBI case agent Robyn Gritz testified Wednesday that U.S. investigators concluded “the Iranian government, most likely the [Revolutionary Guard],” took Levinson.

A longtime friend and business associate, former NBC Nightly News investigative producer Ira Silverman, testified he had helped arrange a meeting in Iran for Levinson with a fugitive American-born assassin whom Levinson hoped to cultivate as a source to advance Levinson’s aim of joining the CIA’s elite operations directorate.

After Levinson’s disappearance, Christine Levinson and their eldest son Daniel traveled to the island, and confirmed Robert Levinson’s signature in the registration records of what was then the Maryam Hotel.

During that trip, Gritz testified, Dawud Salahuddin, who had fled from the United States to Iran in 1980 after assassinating a former aide to the shah of Iran, returned to Levinson’s son a book titled “The Black Dahlia” that Levinson had given Salahuddin at their meeting.

Levinson’s youngest son, Douglas, then 13 and now 26, read an email he wrote to his father four days after he went missing, as FBI agents swept their home for clues.

“hi daddy, im sitting in your den right now crying [ …] please come back home safe and sound, I love you daddy so much. please respond back. please dad im so scared, please come home,” Douglas Levinson read aloud.

Now a Senate Foreign Relations Committee aide — and prone, he said, to anxiety, depression and attention-deficit disorder — he testified, “I still just want him to be home, to be back.”

His sister, too, recited the email exchange about her run for student office.

“hello GURLIE. calling all tortoises! please support Shamanda Turtle in her quest to be vice president of Turtletandia! love Shamanda’s Daddy,” Levinson wrote to her. She wrote back, “i appreciate your support in these important matters and wish you continued success on your weisel deal endeavors. A real tortoise never leaves her fathers emails unresponded. love, daddy’s shaimanda.”