St Catherine were dismissed for 121, then KC replied with177 for eight wickets.
Off-spinner Chris Harrison, two for 10, best supported Dewar, while openers Ajanie Burton (23) and Ricardo Bartley (29) were KC's other leading scorers.
When St Catherine took strike, middle-order batsman Aaron Johnson top scored with 38, while their national Under-17 left-arm spinner, Coi Thompson, took 4-48. The two-day affair will conclude today.
- Jermaine Lannaman