Robert Crockford appeared via audio-visual link from custody in the NSW Court of Criminal Appeal on Friday, where defence barrister Luke Brasch said an alleged "miscarriage of justice" had occurred.

Mr Brasch said his client had been denied a fair trial because of comments made in the Crown prosecutor's closing address to the jury, that "ridiculed and belittled" the defence case - in particular their claim a coughing fit caused the crash.

The 54-year-old was found guilty of all 12 charges including three counts of dangerous driving occasioning grievous bodily harm and seven counts of wantonly causing bodily harm after a trial by jury in the Dubbo District court in September 2020.

Crockford was behind the wheel of a semi-trailer when it ploughed into several cars stopped at roadworks on the Newell Highway, about 20km north of Dubbo on January 16, 2018.

The crash killed Gulargambone's Hannah Ferguson, 19, and her 21-year -old boyfriend Reagen Skinner. It also injured 10 others including a two-year-old infant.

He was sentenced to a minimum of five years and four months behind bars.

On Friday, Mr Brach said the prosecutor should not have told the jury the defence case was full of "lies, inconsistencies and red herrings".

During the trial, the jury were told to consider Crockford had suffered from a condition known as cough syncope, causing him to black out during coughing fits like the one he alleged occurred at the time of the crash.

Mr Brash said the prosecutor in his closing address told the jury the condition was "a myth debunked by proper science" and an "excuse".

During the trial after a witness had given evidence and made reference to cases in the United Kingdom where truck drivers had been acquitted on the basis of cough syncope.

Mr Bransch however said at the closing address, the prosecution told the jury it would be "dangerous to pay attention" to this and suggested the juries in the UK were fooled.

He also argued the crown's closing address did not exhibit the temperament, temper and restraint required - at times making intemperate comments.

In particular the prosecutor's decision to say "your roads" instead of "these roads" when addressing the jury. Mr Brasch said this was an alleged attempt to suggest the jury had "some personal stake" beyond just being objective judges of the facts.

The Crown prosecutor in Crockford's appeal, Brett Hatfield SC, said some of the statements made in the trial "had a hyperbolic aspect to them". He said the comments about the cases from the UK were "inappropriate", but there was no danger of a miscarriage of justice.

"It should have been avoided but given how it was addressed by Her Honour there was no danger of miscarriage of justice by that statement," he said.

Judgement on the appeal has been reserved.