Leicestershire 124 for 4 trail Durham 525 for 8 dec (Steel 224, Richardson 82) by 401 runs
Durham's bowlers drove home the advantage after they had made their highest score against Leicestershire since becoming a first-class county.
The foundation of Durham's imposing 525 for 8 declared was Cameron Steel's 224, the 21-year-old becoming the youngest double centurion in Durham's history.
The California-born Steel, who began the day on 145, reached his 200 off 384 balls, hitting 24 boundaries in the process, before being caught at backward point as the visitors looked to accelerate past 500.
Leicestershire's teenage seamer Matthew Potts then picked up two wickets as the Foxes lost four in the final session of day two of the Division Two match at Grace Road.
The 18-year-old from Sunderland trapped Colin Ackermann leg before with a delivery that stayed low before producing a lifter that Harry Dearden could only edge to third slip, where Tom Latham took a sharp catch in front of his face.
Chris Rushworth made the first breakthrough, knocking Paul Horton's middle stump out of the ground when the experienced opener had reached 38, and had added 62 with Dearden when Leicestershire began their reply.
Aadil Ali was the last wicket to fall - caught behind off Paul Coughlin - as Leicestershire closed on 124 for four, some 401 runs behind.
Having been dropped twice the previous day, by Dearden at second slip on 50 and Ali at backward point on 129, Steel was fortunate again on 165 when Ajmal Shahzad found the edge of his bat with a full delivery, only for Horton to put down a chest-high chance at first slip.
The next ball from Shahzad, a half-volley, was driven for four, and the following delivery from the same bowler, a long-hop, pulled to midwicket for another boundary, a sequence summing up the inconsistency of a Foxes attack missing five senior seamers.
Having failed to take a wicket throughout the first two sessions of the first day, Leicestershire made it three sessions out of four as Michael Richardson and Steel extended their unbroken fifth-wicket partnership to 147 at lunch.
The afternoon session, however, saw a clatter of wickets as Durham began to throw the bat.
One of which was that of Steel, one of four victims for Neil Dexter, the veteran all-rounder marking his return from injury by finishing with 5 for 71, by some margin his best bowling of a much-disrupted season.
He also picked up the wickets of Ryan Pringle, Richardson and Potts as Leicestershire finally found some joy.