Durham 222 for 9 (Jones 87, Conners 3-54, Dal 2-18, Aitchison 2-49) trail Derbyshire 306 (du Plooy 82, Came 78, Dal 56, Rushworth 3-60) by 84 runs
Derbyshire's pace attack put the promotion hopefuls in a strong position on the second day of the LV=Insurance County Championship match against Durham, who could face a possible points deduction after Nic Maddinson's bat was judged to be too big.
England Lions fast bowler Sam Conners took 3 for 54 and Ben Aitchison 2 for 49 to reduce Durham to 222 for 9 at the close with only Michael Jones offering any prolonged resistance with 87.
Allrounder Anuj Dal claimed 2 for 18 in 10 overs as Durham lost five wickets for 26 in the final session to trail by 84.
Umpire Hassan Adnan tested Maddinson's bat with his measurement gauge shortly after the Australian came to the middle but it would not go through and was taken away by match referee Mike Smith. The bat was to be re-examined after the close of play and, if it failed again, would be sent to the ECB to make a judgement.
Derbyshire were docked two points after Mattie McKiernan's bat failed a measurement test in a Royal London Cup game last month.
Maddinson was one of three Durham batters who fell to poor shots after the visitors came through the morning session unscathed.
Conditions looked good for bowling under grey clouds with the floodlights on but the Derbyshire attack, with the exception of Aitchison, served up too many loose deliveries.
Jones's first seven scoring shots were boundaries but Sean Dickson was reprieved on eight when he edged Aitchison low to third slip where Leus du Plooy failed to cling on.
Derbyshire regrouped during the lunch break which was extended by 45 minutes by rain and took four wickets in the afternoon session.
Dickson was the first to go, caught behind carving at the first ball he faced after the restart, and Scott Borthwick also fell to a casual shot when he tried to turn the fast bowler off his legs and got a top edge to square leg.
The bowlers' improved line was rewarded again when the pressure got to Maddinson, who went for a big drive at Dal and was caught at point.
Jones had played responsibly but in the penultimate over before tea, he tried to drive Nick Potts and lost his off stump.
Durham trailed by 164 at the interval but Jonathan Bushnell and Liam Trevaskis frustrated Derbyshire for 19 overs before Conners returned to shift the momentum again.
Conners found enough away movement to have Bushnell caught behind before Trevaskis, badly missed on 21 at third slip, edged to second five overs later where Wayne Madsen knocked the ball up for Brooke Guest to complete the catch.
Paul Coughlin was run out by a direct hit from Potts as he went for a sharp single to midwicket and Tom Mackintosh drove a wide ball from Dal to point.
Conners had Ben Raine caught behind before bad light ended play with Derbyshire well placed to push for victory.
