Eamonn Harrison, 23, told jurors he did not know they had been loaded into the truck he drove to Zeebrugge in Belgium on October 22, 2019.
The group of migrants, which included two boys aged 15, suffocated to death in scorching temperatures inside the sealed truck container.
Their bodies were found in the early hours of October 23 once it had arrived at Purfleet port in Essex, southeast England.
Harrison, from Northern Ireland, has denied 39 counts of manslaughter. He said he was “devastated” for their families and felt “shite” about the deaths.
He is one of four men on trial at the Old Bailey in central London after being charged with involvement in the case.
Georghe Nica, 43, also denies 39 counts of manslaughter, but has admitted being part of a people-smuggling conspiracy.
Alongside Harrison, Valentin Calota, 37, and Christopher Kennedy, 24, have pleaded not guilty to people-smuggling.
Harrison claimed he was unaware of the migrants’ presence despite being busted by U.K. Border Force officials in May 2018 trying to smuggle 18 Vietnamese people into Britain in another trailer.
In that instance he was issued a civil penalty notice.
Prosecutors allege Harrison was involved in two successful smuggling runs on October 11 and 18 last year ahead of the ill-fated trip later that month.
The trial of the four men, which began in early October, is expected to last up to six weeks.
Maurice Robinson, 26, who collected the container in Essex and found the bodies, has already pleaded guilty to 39 counts of manslaughter and to conspiring in people-smuggling.
Haulage firm boss Ronan Hughes, 41, has also admitted 39 manslaughter charges.
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