De La Salle student Fraser Armstrong (18) was airlifted to the UK following the accident at around 11 pm on Easter Sunday.
Two other teenagers were taken to hospital and released a short time later, and a third teenager was discharged last week, it has been confirmed. Further details have also been released about the crash.
A States police spokeswoman said the blue Peugeot 106 was found on its roof by the emergency services after it went through a fence close to the entrance to Simon Sand & Gravel Limited between Le Braye and El Tico.
Officers have spoken to at least five witnesses, not including the teenagers involved.
