510 ILCS 70/4.04
It shall be unlawful for any person to willfully or maliciously torture, mutilate, injure, disable, poison, or kill (i) any animal used by a law enforcement department or agency in the performance of the functions or duties of the department or agency or when placed in confinement off duty, (ii) any service animal, (iii) any search and rescue dog, (iv) any law enforcement, service, or search and rescue animal in training, or (v) any accelerant detection canine used by a fire officer for arson investigations in the performance of his or her functions or while off duty. However, a police officer or veterinarian may perform euthanasia in emergency situations when delay would cause the animal undue suffering and pain.
A person convicted of violating this Section is guilty of a Class 4 felony if the animal is not killed or totally disabled; if the animal is killed or totally disabled, the person is guilty of a Class 3 felony.
510 ILCS 70/4.04