The jury in the Joanna Yeates murder trial is considering its verdict for a second day.
Mr Justice Field has urged the six men and six women trying her neighbour Vincent Tabak to reach a unanimous verdict.
The defendant, 33, denies murder but admits the manslaughter of Miss Yeates, 25, at her flat in Clifton, Bristol.
The judge said the jury needed to focus on what Tabak's intention was at the time she died.
The jury resumed deliberations after spending three hours yesterday considering its conclusion.
The judge asked the jury yesterday: "Did he intend to kill her or cause her really serious harm?"
"The fact that afterwards the defendant may have regretted what he had done does not amount to a defence.
"If having examined the evidence, and despite the defendant's denial, you are sure that when the defendant strangled Joanna Yeates he intended to kill her or cause her really serious bodily harm, your verdict will be guilty.
"If you are not sure of his intentions when he strangled Joanna Yeates, your verdict should be not guilty."
The jurors "should not allow emotion" or sympathy towards Ms Yeates's family and boyfriend Greg Reardon to cloud their judgment when making their decision, Mr Justice Field added.
He told them: "The defendant is charged with murder - the most serious charge in the calendar of the criminal law.
"Please do not allow emotion to enter into your deliberation.
"This is a tragic case. A lovely young woman, with a promising future ahead of her, has been robbed of her life.
"Her death will have, and doubtless continues to have, a devastating effect on her family and Greg.
"You must not allow emotion or sympathy for Joanna and her family and for Greg to cloud your judgment."
Landscape architect Miss Yeates was last seen alive on the evening of December 17 last year.
She was reported missing two days later when her boyfriend returned to their ground-floor flat in Canynge Road after a weekend away.
Police launched a massive hunt for the university graduate but her body was found by dog walkers on Christmas morning in a country lane in Failand, North Somerset - just three miles from her home.
The net closed in on Tabak and he was arrested on January 20 when police matched his DNA to samples found on Miss Yeates's body and clothing.
The jury was sent home and will resume its deliberations tomorrow.