Lawes is understood to have a minor injury niggle, while Augustus hasn't recovered from the knock that forced him off against Saracens last weekend.
That means Tom Wood and Harrison start in the back row.
It will be Harrison's first appearance for Saints since the defeat to Leicester Tigers at the end of October as he has been recovering from a hamstring injury.
Freeman is back from a shoulder injury and the versatile back takes his place on the bench at Kingston Park.
Ollie Sleightholme will not be involved, meaning Tom Collins is handed a rare start, his first since the defeat to Harlequins in mid-November.
Piers Francis has been ruled out after suffering a foot injury against Saracens last weekend, so Fraser Dingwall returns at centre.
As for Newcastle, they include a couple of former Saints players in their starting line-up, with Joel Hodgson at 10 and Luther Burrell at 12.
However, the Falcons are without key wing Adam Radwan, who is having to isolate.
Newcastle Falcons: Brown; Penny, Orlando, Burrell, Carreras; Hodgson, Schreuder; Cooper, McGuigan, Davison; Peterson, Robinson; van der Walt, Welch (c), Chick.
Replacements: Blamire, Brocklebank, Tampin, Fearns, Graham, Stuart, Connon, Wacokecoke.
Saints: Furbank; Skosan, Dingwall, Hutchinson, Collins; Biggar, Mitchell; Waller, Matavesi, Hill; Ribbans, Ratuniyarawa; Wood, Ludlam (c), Harrison.
Replacements: Fish, Iyogun, Painter, Coles, Wilkins, James, Litchfield, Freeman.