The appointment of deputy sheriffs in the Police Department, full-time deputy sheriffs not employed as county police officers or county corrections officers and of employees in the Department of Corrections shall be made from those applicants who have been certified by the Board as being qualified for appointment. Certification for appointment in one department shall not constitute certification for appointment in another department. Certification may be made at any point prior to appointment and may be made in conjunction with the Sheriff’s application process. All persons so appointed shall, at the time of their appointment, be not less than 21 years of age, or 20 years of age and have successfully completed 2 years of law enforcement studies at an accredited college or university. Any person appointed subsequent to successful completion of 2 years of such law enforcement studies shall not have power of arrest, nor shall he or she be permitted to carry firearms, until he or she reaches 21 years of age. Any person appointed shall be a citizen of the United States, an individual who is legally authorized to work in the United States under federal law and is authorized under federal law to obtain, carry, or purchase or otherwise possess a firearm, or an individual against whom immigration action has been deferred by the U.S. Citizenship and Immigration Services under the federal Deferred Action for Childhood Arrivals (DACA) process and who is authorized under federal law to obtain, carry, or purchase or otherwise possess a firearm. In addition, all persons so appointed shall be not more than the maximum age limit fixed by the Board from time to time, be of sound mind and body, be of good moral character, have not been convicted of a crime which the Board considers to be detrimental to the applicant’s ability to carry out his or her duties, possess such prerequisites of training, education and experience as the Board may from time to time prescribe, and shall be required to pass successfully mental, physical, psychiatric and other tests and examinations as may be prescribed by the Board. Preference shall be given in such appointments to persons who have honorably served in the military or naval services of the United States. All appointees shall serve a probationary period of 12 months and during that period may be discharged at the will of the Sheriff. However, civil service employees of the house of correction who have certified status at the time of the transfer of the house of correction to the County Department of Corrections are not subject to this probationary period, and they shall retain their job titles, such tenure privileges as are now enjoyed and any subsequent title changes shall not cause reduction in rank or elimination of positions.