Jurors in the trial of alleged killer Greg Lynn have been told they cannot find the former Jetstar pilot guilty of manslaughter.

The alternative charge of manslaughter had been mentioned to jurors at the outset of the weeks-long double murder trial.

But as Justice Michael Croucher’s summing-up of the case began in the Supreme Court of Victoria on Thursday, he told jurors the circumstances of the case meant that if they were not satisfied beyond reasonable doubt of the murder charges, “any verdict of manslaughter in the alternative would be wrong”.

“The only charges before you are murder, and it’s for you to determine whether Mr Lynn is guilty or not guilty in relation to [Russell] Hill and whether Mr Lynn is guilty or not guilty in relation to [Carol] Clay,” the judge said.

Mr Lynn, 57, is accused of murdering retirees Russell Hill and Carol Clay at the remote campsite they shared in Victoria’s High Country in March 2020.

Both prosecution and defence lawyers agree the former Jetstar pilot tried to cover up his involvement in their deaths by setting fire to their campsite, altering his car and returning to the remote track where he dumped their bodies to set fire to their remains.

Weeks-long murder trial draws to a close

Nearly 50 people have given evidence on topics as broad as shotgun shell trajectories, telecommunications data and Mr Hill’s amateur radio use as they were called to the witness stand across about four weeks.

“It might be said we’re in the home straight,” Justice Croucher said, before giving jurors an overview of the defence and prosecution cases.

Led by Daniel Porceddu, prosecutors argued they did not know the motive or precise circumstances of the pair’s deaths, other than that Mrs Clay was shot in the head.

But they argue Mr Lynn’s conduct afterwards could only be explained by a belief he had murdered the pair.

“This subsequent behaviour, if committed in the belief that he had murdered Mr Hill and Mrs Clay, is conduct the law calls incriminating conduct,” the judge explained in summing up the prosecution case on Thursday.

Defence lawyers, led by Dermot Dann KC, argued the pair’s deaths were tragic accidents that followed separate struggles between Mr Hill and Mr Lynn for control over a knife and Mr Lynn’s 12-gauge shotgun.

“In each case, submits Mr Dann, Mr Lynn’s account of the accidental killings is consistent with numerous other items of evidence,” the judge said.

Defence lawyers argue the lack of evidence in relation to the deaths, and Mr Hill’s in particular, means Mr Lynn must be found not guilty.

The judge told jurors to ignore any media coverage, abstain from any research and overlook any sympathy, bias or prejudice as they determined the case.

He said that included ignoring any “great sympathy” they may naturally feel for the deceased lovers or their loved ones, any belief their secret affair was “morally wrong” or any feeling that Mr Lynn’s behaviour in covering up their deaths was “terrible”.

“You must weigh the evidence logically and with an open mind, and not according to your passions or feelings or personal judgements about what is morally acceptable or morally unacceptable,” the judge said.

“Your function and your duty is to use your heads, not your hearts.”

The judge’s summing-up of the trial is expected to continue throughout Thursday.