A haulage boss accused of being linked to the deaths of 39 migrants tried to stop his mother "gossiping" after news of the tragedy broke, a court heard.
Caolan Gormley, 26, denied involvement in an unlawful immigration plot with his former boss Ronan Hughes and truck driver Christopher Kennedy.
Giving evidence on Tuesday, Mr Gormley told jurors he thought they were engaged in smuggling alcohol rather than humans.
The trial is ongoing at the Old Bailey.
Mr Gormley, of Caledon, County Tyrone, told of his "shock" and "total disbelief" when 39 Vietnamese men, women and children were found dead in one of Hughes's vehicles in Essex early on 23 October 2019.
He said he saw the breaking news on social media then someone sent him a photograph of the truck and trailer on WhatsApp, which he sent on to Kennedy. He then spoke to Hughes.
Mr Gormley said: "He called me the night before and I was returning the call. I remember when he answered he sounded different, panicked, making no sense at all. It was just mumbo jumbo."
At 15:46 on 23 October, Mr Gormley received a text from his mother asking if the truck in the news belonged to one of Hughes' brothers.
He replied: "Don't know and neither do u (sic)."
Asked to explain the message, Mr Gormley said: "My mother works in a doctors' surgery and is a bit of a gossip, and I didn't want her gossiping. Perhaps there would be repercussions for her."
Defence barrister Stephan Alfred asked: "You thought it would be unsafe for her bandying names about?"
Mr Gormley replied: "I mean talking about that in general, you wouldn't want people going around talking about it."
He added that he never heard anything bad about any member of the Hughes family until the migrant deaths.
Mr Alfred suggested the tragedy had sent a "shockwave through the industry".
Mr Gormley said there was "total disbelief this had happened", adding: "I was just shocked, to be honest."
Jurors have been told that a number of individuals have already been convicted of their part in the people-smuggling operation.
Hughes and Romanian Gheorghe Nica were said to have been in charge of a network of drivers "willing and able" to take lorry loads of migrants to the UK.
Mr Gormley denies a single charge of conspiracy to assist unlawful immigration. The trial continues.