Appeal from the Circuit Court of the 12th Judicial Circuit, Will County, Illinois, No. 00-CF-1986 Honorable Gerald Kinney, Judge Presiding.
 The opinion of the court was delivered by: Justice Lytton
 Defendant Paul F. Runge was charged in a multi-count indictment with various offenses committed during an October 6, 2000, escape from the Department of Human Services (DHS). Defendant pleaded guilty to escape (720 ILCS 5/31--6(b-1) (West 2000)); and, following a bench trial, he was convicted of armed robbery (720 ILCS 5/18--2(a)(1) (West 2000)), two counts of aggravated battery (720 ILCS 5/12--4(b)(8) (West 2000)) and two counts of possession of contraband in a penal institution (720 ILCS 5/31A--1.1(b) (West 2000)). The trial court sentenced defendant to an aggregate term of 90 years' imprisonment. Defendant appeals, arguing that (1) the State failed to prove him guilty of armed robbery beyond a reasonable doubt; (2) his convictions of armed robbery and escape violate one-act, one- crime principles; (3) the offense of escape from the custody of DHS violates constitutional equal protection guarantees; (4) he was not proved guilty beyond a reasonable doubt of possession of contraband based on possession of a cannister of pepper spray; (5) the cause must be remanded for compliance with Supreme Court Rules 605(b) and 604(d); and (6) the court was not authorized to impose consecutive sentences for armed robbery and two counts of possession of contraband. We reverse in part and remand for further proceedings.
 On May 28, 2002, defendant entered a plea of guilty to the charge of escape. The State's factual basis established that on October 6, 2000, defendant resided in the DHS facility of Sheridan Correctional Center (SCC) pursuant to the Sexually Violent Persons Commitment Act (725 ILCS 207/1 et seq. (West 2000)). Defendant and another resident, Gregory Conley, escaped while they were being transported from the Sheridan facility to Chicago for court proceedings. Following admonishments, the court accepted defendant's guilty plea. Defendant then waived his right to a jury trial on the remaining charges.
 At trial, DHS security aide Rick Schroeder testified that he was assigned to drive three residents from SCC to Chicago for court proceedings on October 6, 2000. He described the DHS treatment and detention facility as physically located in the center of SCC. To leave the facility, DHS residents had to pass through a portion of the prison. Schroeder said he and security therapy aide Manessa Nelson loaded the three residents into the van and left SCC early in the morning.
 When they reached Plainfield, Conley appeared to be sick. Conley asked permission to move to the front seat. He was allowed to do so. Schroeder said someone called his name when they reached a stop light, and he turned his head to respond. Schroeder next felt his face being sprayed with pepper spray. He said his eyes "slammed" shut. He managed to park the van and get out. After regaining sight out of one eye, Schroeder found Nelson standing outside the van coughing. Defendant and Conley were gone, and the third resident, George Timmons, was coughing with his head sticking out of a broken window.
 Schroeder also testified that DHS issued clothing for the residents to wear when they went to court. He identified articles of clothing worn by defendant and Conley on the date of the offenses as property of DHS.
 Naperville police officer Greg Bell testified that he responded to a radio dispatch to be on the lookout for the escapees around 8 a.m. on October 6, 2000. He spotted a four-door sedan bearing the license plate number broadcast in the dispatch. After Bell stopped the vehicle and placed its three occupants under arrest, a gun in a case was removed from the front floorboard of the car.
 State Police Special Agent Vic Markowski testified that he interviewed defendant at the Naperville Police Department on the evening of October 6, 2000. Defendant stated that former DHS employee Doris Harper and Amber Waller, a security therapist aide at the DHS facility, had given Conley and defendant a handcuff key and two cannisters of "mace" to facilitate their escape. The plan was to have Conley feign illness en route to Chicago and ask that the volume of the radio be turned up in the van so that their DHS escorts would not hear the escapees removing their hand and leg restraints. Defendant admitted that he had a cannister of "mace" and the handcuff key on his person when he boarded the van. However, he denied that he used the "mace" when he and Conley escaped.
 State trooper Glenn Strobel testified that he inventoried the contents of the getaway vehicle on October 6, 2000. In addition to the gun and case identified by Bell, Strobel found a shank, DHS clothing that had been issued to defendant and Conley the morning of the offense, shackles, a handcuff key and a cannister of Saber pepper spray.
 Larry Olson, a crime scene investigator for the State police, testified as an expert with regard to the cannister of pepper spray. He stated that the pepper spray cannister recovered from the rented vehicle contained a non-lethal noxious liquid gas commonly known as "mace." The item was the kind of device generally available in retail stores for personal protection and not the kind used by law enforcement officials.
 Following closing arguments, the trial court found defendant guilty of robbery, armed robbery, two counts of aggravated battery and two counts of possession of contraband ("mace" and a handcuff key) in a penal institution. The court subsequently sentenced the 32-year-old defendant to consecutive prison terms of 60 years for armed robbery and 15 years for each conviction for possession of contraband. The court also imposed concurrent sentences of seven years for escape and five years for each aggravated battery--these sentences to be served concurrently with the armed robbery sentence. The court ruled that the robbery conviction merged with the armed robbery conviction. Consequently, the court did not impose sentence on the lesser offense. Defendant filed a motion to reduce sentence, which was denied, and he appeals.
 Defendant was charged with robbery by taking the DHS-issued clothing he was wearing from the presence of Schroeder and Nelson by the use of force. He was charged with armed robbery by taking the clothing from Schroeder and Nelson by the use of force while carrying a knife. Defendant now challenges the sufficiency of the State's proof that (a) force was used as a means of taking the clothing from DHS, and (b) he or one of his accomplices carried a knife. He argues that his armed robbery conviction must be reversed outright because there was no concurrence between his use of force and his taking of the clothing. ...