The lawyer for double-murder accused Chris Kahui has delivered her parting words to the jury at the High Court in Auckland.

Lorraine Smith has finished her closing address at Kahui's trial for the murders of his three-month-old babies Chris and Cru, who died in June 2006.

Kahui's defence team say the police failed to properly investigate the twins' mother Macsyna King and ignored crucial evidence while they pursued him.

Lawyer Lorraine Smith ended her more than four-hour closing address, by saying to the jury "this trial has taken six weeks out of your life, but you are dealing with Chris Kahui's whole life. Please be careful with it."

The judge was due to begin summing up at 11.30am.