THC was also found in his system though he denies smoking cannabis that night and suggested it could have been from second-hand smoke.
Johnson was then convicted of dangerous driving.
The judge noted that if he'd simply fallen asleep at the wheel and no substances had been found in his system then he could not have been convicted of dangerous driving.
In New Zealand law it must be proved that a person's dangerous driving is due to some fault of the driver that caused the situation, or in this case the crash.
Falling asleep at the wheel does not constitute dangerous driving unless it can be proved the driver made themselves fall asleep.
Johnson then appealed his conviction and his lawyer argued that it couldn't be proved MDMA had been the cause of him falling asleep.
In a High Court decision released recently, Judge Cameron Mander found that just because someone has taken MDMA doesn't by default make their driving dangerous.
"However, I do not consider in the circumstances of this case there can be any issue that Mr Johnson's driving was dangerous."
"The simple fact of his failure to negotiate the intersection safely and, indeed, to drive through it at speed and crash is an obvious example of dangerous driving."
He went on to say that the cause of the crash was that Johnson had fallen asleep - but what was crucial to understand was if he realised that driving while tired, was dangerous.
"As I have already accepted, the deliberate ingestion of MDMA alone, at least without the benefit of expert evidence, will not establish a level of impairment that either can be acquainted with the act of dangerous driving or, relevantly to the present case, can necessarily be linked with falling asleep."
In his conclusion Judge Mander found that there was no evidence to suggest a link between taking MDMA and Johnson falling asleep and quashed his conviction.
