One of the seven Vietnamese migrants rescued from a van on a Dieppe to Newhaven ferry suffered a stroke in the cramped air-starved conditions.
He was taken to hospital after being rescued from the hidden section in a Ford Iveco Sprinter but suffered a “life-limiting” stroke.
It is believed to be the direct result of the terrible conditions, a Home Office official said.
Six men and one woman were rescued from the concealed section “the width of a human chest”, after they were heard screaming for help as they were starved of oxygen and became dehydrated.
Anas Al Mustafa, 43, has been convicted of assisting unlawful migration by trafficking the seven people in a specially adapted van on Friday 16 February.
The discovery at the port sparked a major emergency services response. Ambulances, police and Border Force attended and all the migrants were taken to hospital and treated.
After the jury returned a unanimous verdict, Nick Corsellis, prosecuting, said that the younger migrants had recovered well from the dehydration and heat.
But one man had a possible heart attack, one woman had acute kidney injury and another man went to hospital in a comatose state and suffered a stroke.
Outside court, a Home Office official, Chris Foster, the regional lead for criminal investigations in London and the south, said: “Frankly, how somebody didn’t die I don’t really know.
“They were very fortunate overall but that has nothing to do with Mr Al Mustafa. He is the man responsible and (this verdict) sends a really strong message.”
He added that while six of the migrants had made a full recovery, the man who had a stroke suffered “life-limiting” effects as a result of it.
Mr Foster said: “Unfortunately, one of the men suffered pretty much a life-lasting effect.
“He suffered a stroke that we believe to be as a direct result of being held in that van and, even today, now, he has difficulty walking and he suffers with memory loss. So it is life-limiting for him.”
He said that six of the migrants had applied for asylum in the UK and an investigation was continuing into further involvement of others in the case.
He said: “We will work night and day to bear down on the criminal gangs that destroy our immigration laws and undermine our borders.
“In this country, we provide a safe haven for those that come here who are fleeing persecution and there are regularised routes for doing that.
