A senior constable is senior to a constable but junior to an incremental senior constable, you can be promoted after 4 years as a constable (5 years of service) to senior constable upon passing probity checks and an exam.
A senior constable is senior to a constable but junior to an incremental senior constable. Promotion to Senior Constable can occur after a miniumum of 5 years service, one year as a one year as a Probationary Constable in addition to 4 years as Constable and then upon passing probity checks and an exam.