A North Korean defector was acquitted Thursday by a Seoul district court of espionage charges, accusations initially made by his sister, who said she and her brother had been recruited to spy by the North’s secret police.

Until his arrest eight months ago, Yoo Woo-sung had been among the most well-connected and trusted of the 24,000 defectors from North Korea now living in the South. Yoo, 32, held a job at Seoul City Hall and coached fresh arrivals about their bustling, sometimes bewildering new home country.

His arrest rattled the defector community and raised concerns among activists about the methods that South Korea uses to weed out spies from defectors.

In the past five years, South Korea has arrested 14 defectors as spies, a group that includes would-be assassins and temptresses seeking military secrets.

But Yoo’s case had an unusual twist: He was accused by his sister, Yoo Ga-ryeo, as she was trying to defect from North Korea and was being investigated by South Korean intelligence agents.

All new arrivals from the North go through an intensive screening process, and three years ago, the South doubled to six months the period allowed for interrogations.

Yoo Ga-ryeo had been held in near-solitude for weeks when she described for the South Korean agents a sibling spying mission — one that she’d later say she fabricated under duress.

According to Yoo Ga-ryeo’s initial story, her brother was coerced into working for the North’s security agency, the Bowibu, which vowed to retaliate against his family — still in the North at the time — if he didn’t cooperate.

Yoo Ga-ryeo said her brother was asked to infiltrate defector groups in the South and send back information on the escapees. She told the South Korean agents that she helped transmit the information — going to Internet cafes just over the Chinese border, corresponding with her brother, then returning to the North.

But Judge Lee Buhm-gyun said he found Yoo Ga-ryeo’s testimony to be inconsistent, implausible and unreliable. Prosecutors failed to find evidence on her brother’s computer, he said. He also noted that information can be passed to the North without the risky border crossing described by Yoo Ga-ryeo.

After Lee announced the not-guilty verdict in a packed courtroom, Yoo Woo-sung wept and hugged one of his attorneys. Later in the afternoon, he was released from the Seoul Detention Center, where he has been held for eight months and allowed one visitor per day.

Yoo must still contend with some smaller legal problems related to his entry to the South in 2004, when he told its authorities that he was a North Korean citizen.

Yoo is, in fact, a Chinese citizen — born in North Korea but raised by Chinese parents. Because of his false claim, he qualified for South Korean government funding for resettlement, university tuition and living expenses.

Yoo admitted to the deception during the court proceedings, saying he was “very sorry.” The judge ruled Thursday that Yoo must pay back the roughly $22,000 he received from the government and gave him a one-year prison term with two years suspended, meaning that he won’t have to serve the term if he commits no crimes during that two-year period.

Yoo’s sister, who is also a Chinese citizen, was deported to China in June.