As German shepherds yelped in their squad car cages and police helicopters whirred overhead, Sgt. Benjamin Cohey, at 6-foot-7 and 265 pounds, carved out sections of a 10-mile area where the men and dogs of the state police would hunt down a band of escaped convicts from the Maryland House of Correction.

"How do you know what they look like?" asked a trooper, interrupting the sergeant's gruff instructions.

"Anybody you see, you stop," barked Cohey. "If they don't have any ID, you call and ask for an identity check. If you can't identify them, bring 'em in."

From predawn to dusk today, Cohey's men and more than 100 other state policemen and county officers roamed the highways and woods from Baltimore to Washington in a sometimes easy, sometimes wild, and now and then crazy effort to "bring in" 30 prisoners on the lam.

[By early Friday, 21 of 30 escapees had been recaptured and police were still looking for the other nine.]

Many of the escaped prisoners were easy pickings for the posse of lawmen, particularly the dozen or so who were found trying to hitchhike or walk up the road to their old haunts in Baltimore. One escaped prisoner even attempted to rob a bank within hours of gaining freedom and was caught in the act. Others were sniffed out of the woods by the dogs or plucked from fields by the helicopters.

The police would parade the handcuffed prisoners before the press as they took them off to jail and Lt. B. T. Hayward kept crossing each new capture off his list of 30 escaped men.

But it was not always that simple.

At mid-afternoon, 10 miles from Jessup, six state troopers began sprinting down the railroad tracks. Canine handlers Farmer, Love, Lowery and Payne held their anxious dogs at the end of eight-foot leashes and fanned out in the underbush.

"They went into the pines up ahead," shouted trooper Vernon Love into the radio strapped to his shoulder. Two troopers scampered down a culvert into a backyard vegetable garden and found tracks in the loose mud and asphalt.

"I've been here 20 minutes and I haven't seen a thing," said a befuddled John Little, a retired man who was observing the seemingly dramatic chase. "But my Chesapeake retriever's been raising hell since four in the morning."

At that moment, Trooper Larry Farmer shouted: "I just saw two guys run across the tracks."

Farmer and the other dog handlers sprinted in the direction where the suspects had been sighted. Seconds later, the two suspects emerged from the brush. They had beaming grins, and announced that was great fun leading the troopers on a wild goose chase.

The police, flushed with anger, ordered the two teen-agers home to their parents.

"They thought it was funny," fumed trooper Payne, who was still out of breath from the chase and was holding back his dog, Max. "If I'd caught 'em in the woods and let Max after 'em, they wouldn't have been laughing. Of course, I would have had 14 days of reports to fill out. I hate paper work."

As the day wore on, police managed to catch a lot more than teen age pranksters. By 5 p.m., state troopers were marching into the Jessup command post with two handcuffed men -- numbers 19 and 20 in the tally of captured prisoners.

A helicopter and trained dogs had flushed these men out of the woods near the Baltimore-Washington Parkway about three miles south of Jessup. The helicopter and the canine units had rushed to the area after armed police had spotted some suspects in the woods.

Aboard one helicopter, state police were trying out a sophisticated infra-red heat sensor that can find people on the ground by detecting their body heat even though they are obscured by foliage. It didn't detect any escaped prisoners today.

During the day police even managed to bring in a bonus prisoner, Larry E. Duvall, who escaped Saturday from the Anne Arundel Detention Center. Filled with pride at his catch, Frank Seib, a deputy sheriff from faraway Allegany County, said his dog Toby had flushed the man from nearby woods and into range of the drawn revolvers of two police officers.

"When I put him on the man, I had no idea if Toby was going to track him or go play in the woods," said Seib. "But when he started pulling me through the stream and into the woods, I knew I had something."

"Good work, Frank," said Sgt. Cohey, patting the trooper on his sweaty back.

"I was kind of down in the dumps until now," said Seib, a lowly deputy sheriff in the midst of elite troopers and one of four students Cohey brought down from Easton, where he teaches K-9 classes at the state police training school. "I'd just been tagging along till now."

But many of those at the command post were not newcomers to manhunts.

Capt. Gary Moore, for instance, chief of the state police aviation division, talked knowledgeably of how his helicopters with their sweeping white searchlights had kept the escapees in the woods near Jessup through the night.

"We held them there till daylight," said Moore who had been told by one of the captured men that some of the prisoners were afraid the helicopters would find them if they left their forest refuge.

As daylight came, the canine teams went in and routed several prisoners from the woods, sending them into the waiting arms of state troopers.

Many had been caught that way, but others had been captured as far away as Baltimore or on the Beltway around Washington.

Seven suspects even were sighted in Catonsville south of Baltimore, where a 13-year-old girl had been terrified by two men who came to her front door and shouted: "Open the door or we'll blow the hinges off," according to police.

The girl, Tia Pollock, instead ran to the phone and called police, saying she had sighted not only the two suspects, but five more waiting in nearby woods.

After a search that lasted several hours, however, no men were captured in the area.

Back at the command post, the high drama played all day long to its own peanut gallery. A social gathering of 10 residents from Tall Pines Trailer Park dragged lawn chairs, radios, dogs and soft drinks to a grassy rise besides the firehouse. They said it was better than watching the TV soap operas.

"We just hope it won't end like the soaps -- continued until tomorrow," said housewife Ruth Harrison. "We hope the police catch them all and that will be it."