Because he took a college course on the geography of crime, Sgt. George Rogers, of the Baltimore County police tactical squad, knew the value of using a computer to track crimes.
But even he was slightly surprised about the effectiveness of a sophisticated new software package that the city and county police used to investigate the shotgun-robbery cases this month.
"Everything just kind of froze for a moment," said Rogers, describing the officers' reaction to the mapping program. "You could actually see through the smoke and discern a pattern."
"Within a matter of hours, we had patterns on these guys," Rogers continued. "Had we plugged in sooner, we might have got these guys sooner."
The software, called Map Info, allows police to plug in information about each crime -- date, time, location and other data, such as the number of suspects, the types of weapons used, whether victims were attacked, even whether a robber took a pillow case to carry the loot. Then, the information is plotted on a computer map.
It's one of the newest, and most powerful, tools in the hands of local police. In the shotgun-robbery cases, it was the first time the city and county joined forces to use the technology.
Several officers said yesterday they believe the use of computers to track crimes will help police nail burglary suspects by their patterns, plot drug markets and predict areas of high crime, thus allowing them to beef up enforcement in those areas.
With the arrest of several suspects in connection with a number of the shotgun holdups, police are pretty sure -- but not certain -- that the core group of shotgun bandits has been broken up.
"It's too early to tell for sure," said Sgt. Stephen Doarnberger, a county police spokesman. "But we're hopeful."
"The leaders, the organized crime, if you will, has been stopped," Rogers said. "We hope that's pretty much the end of this rash."
The last two robberies matching the pattern happened over the weekend, but police believe those incidents were the work of copycat groups, not the original group.
Although police are reluctant to reveal everything they have learned about the string of armed robberies -- 94 in all, stretching back to last October -- they say that despite great efforts to make the robberies appear to be at random, patterns emerged.
For instance, the software indicated areas of the city and county that were not hit, allowing police to concentrate their stake-out efforts in the areas hit most often.
Once the city and county robberies were both entered into the computer, it became clear that the robbers were hitting the city on certain days and the county on other days, within certain time frames.
At his computer terminal at police headquarters in Towson yesterday, Philip R. Canter, supervisory statistician for the county police, punched up several computer maps that displayed where the robberies occurred.
"We can do this by any variable," he said, displaying maps of robberies that occurred only on Thursdays, then robberies that occurred only on the third and fourth weeks of the month between the hours of 5 and 11 p.m.
The police began using the computer at the beginning of March, said Canter, with his staff producing maps of different areas that police in the city and county carried with them into the field.
"The amount of cooperation between the two agencies was just incredible," Canter said. "We had a common goal. We wanted to catch these guys."
One of the suspects arrested, Eric Cornell Wheeler, 29, may have been arrested because of computer matching.
Wheeler is accused of holding hostage more than 13 employees of a Towson credit union in the aftermath of an armed robbery there March 7.
While police were not able to predict that the State Employees Credit Union would be hit that day, they had more patrols in the area because the pattern dictated a robbery in the county.
"We heard it right when it came down," said Canter, who was driving in his car at the time. "It fit the pattern. We were real pleased with that."
Quick response by police was one reason one arrest was made, even though four men escaped. A suspect ended up running back into the building and then later surrendering. All the hostages were released unharmed.
"This technology is so dynamic," said Rogers, "it's probably one of the hottest things I've seen in my 17 years of law enforcement."