55 ILCS 5/3-7009
Promotion of deputy sheriffs in the County Police Department, full-time deputy sheriffs not employed as county police officers or county corrections officers, and of employees in the County Department of Corrections shall be made by the sheriff from those candidates who have been certified to him as being qualified for promotion. Certification for promotion in one department shall not constitute certification for promotion in another department. The Board shall make certifications for promotions on the basis of ascertained merit, experience and physical, mental and other tests and examinations. Those promoted shall serve a probationary period of 12 months and during that period may be reduced to their former rank at the will of the Board. Employees of the house of correction whose names, at the time of the transfer of the house of correction to the County Department of Corrections, appear on a civil service promotional register, shall retain the same status insofar as their eligibility to comparable positions in the employ of the County Department of Corrections is concerned.
55 ILCS 5/3-7009