The jury in the trial of a 50-year-old man accused of murdering his alleged "love rival" and putting his body in an underground tank will resume its deliberations tomorrow.

Patrick Quirke denies murdering part time DJ, Bobby Ryan, known as "Mr Moonlight" so he could rekindle his relationship with Mr Ryan's girlfriend, Mary Lowry.

Ms Justice Eileen Creedon told the jurors they had to be objective and dispassionate and should not be influenced by emotion, sympathy, anger or disgust.

More than three months after the trial began, Ms Justice Creedon told the jurors they had reached the last stage in the process.

She said the facts in the case were for the jury to decide. 

But she had to tell them about the rules they had to apply.

The judge told the jurors, they could draw inferences from the evidence but must not speculate.

She said circumstantial evidence could be powerful, but they must examine it with care and consider if it was reliable and if it proved guilt. 

If there was another rational explanation consistent with innocence, they must acquit.

She reminded them the onus was on the prosecution to prove the case. An accused person did not have to give evidence and that could not be held against them.

The jurors could only convict Mr Quirke she said if they were confident it was the right decision and they had no reasonable doubt. 

They had to be satisfied he killed Bobby Ryan unlawfully and that he had intended to kill him or cause serious injury to him.

This afternoon the jurors began their deliberations.

They have been provided with memos of interviews and phone records and will be able to view material on a screen in their jury room. 

They will continue their deliberations in the morning.