Officers Jennifer Roh and Andrea Davidson, responding to a call about a grocery store robbery, seemed confused.

One customer lay wounded and another customer, the store owner and employe were shouting conflicting descriptions of the assailant.

"He was tall," said the customer.

"No he was . . . short . . . about 5 foot-six" said the owner.

"Talk to me, I saw the whole thing," said the employe.

"Okay you go call the police," Roh said nervously.

"But you ARE the police," the employe wailed.

Well, not really.

Roh, 16, Davidson, 17, and the store occupants are all students from Prince George's County high schools participating in a mock police incident. The unrehearsed exercise was a feature of the 10th Annual Law Conference Day sponsored by the county public schools and the county Bar Association. It was held at Prince George's County Community College last week.

"Police patrol simulation" was the action part of a day that began with finals for a mock trial competition. Students came to learn about law enforcement and meet police officers, said school spokeswoman Jacquelyn L. Lendsey. High schools each sent 10 participants.

Representatives of the county police, sheriff's department, U.S. Park Police and Maryland State Police were on hand to offer pointers as crime scenarios unfolded.

"Your first responsibility is the safety of those individuals and yourself," said State Trooper James Downing as he assessed the way the officers had investigated the grocery store holdup. "Once everything is secured, your attention should go to the wounded person.

"I would also separate the witnesses to get individual accounts of what happened."

Davidson, a student at High Point High School, said being an officer for the day had given her greater respect for the police.

"I didn't know it would be so difficult. I'll be more sympathetic to them now," she said.

"Students don't usually actually come in contact with police unless they're pulled over for a traffic violation . . . or have done something else wrong," Lendsey said. "We want to show students that the police are here to protect us and provide for our safety."

Officers also talked about what it takes to be in law enforcement.

"Police work has changed from the 'good ole boy' days when all you needed was a rifle and a pickup truck," said Sheriff's Department Cpl. Alan Dunivant. "Today, many police officers have a college education."

In another mock incident, Anthony Talbert of Crossland High and Jeff Gurman of Highpoint portrayed officers who had stopped a car full of drunk teen-agers. One student bolted while Gurman was frisking him and a chase ensued around the conference room.

Later, after the capture, Gurman was asked how he felt when the offender escaped. "All I wanted to do was catch him," Gurman said.

"One of the common feelings among police officers is frustration," Cpl. Elizabeth Mints told the students.

"We're all human and some days we wake up in a bad mood . . . and 'concerned' and 'fair' drop out the back door," Dunivant said.