Daniel Boulton, 30, of Alexandra Road, Skegness, denies murdering Bethany Vincent, 26, and her nine-year-old son Darren Henson.
Their bodies were found dead at a house in High Holme Road, Louth, at 8.29pm on 31 May. Both had suffered stab wounds.
Boulton also denies assaulting PC Stephen Dennis with intent to resist arrest on June 1, and a further offence of burglary at Hubbards Hills Cottage in Halfpenny Lane, Louth, where it is alleged clothing, food and drink were stolen between 30 May and 2 June.
Twelve jurors were this morning (Thursday) sworn in at Lincoln Crown Court, along with two reserves.
The case is expected to be opened later this afternoon.
The trial in front of Mr Justice Pepperall is expected to last three to four weeks.