In hot pursuit of a driver with stolen plates one recent night, four Charles County deputies suddenly found they had unwanted company -- two Maryland state troopers who came out of nowhere to join the chase, trying to pass the deputies and the suspect at speeds of more than 90 miles per hour.

"We've got two Maryland State Police units coming up behind us to see if they can get in front," an exasperated deputy radioed to headquarters. Three times the supervising lieutenant told the troopers to "back off." Each time they ignored him.

It was law enforcement Charles County style, where the county's astounding growth seems only to have exacerbated a long-standing rivalry between the state police and the local sheriff's department. Once, the state troopers were the law. Lately, they have been shunted aside, reduced to little more than traffic cops, as the sheriff's department has evolved as the main law enforcement agency.

It's a change that some troopers have been reticent to accept.

Former Charles County sheriff James Gartland, who engineered a 1994 agreement that gave the sheriff's department jurisdiction over most criminal investigations, believes the continuing tension between the two agencies is affecting the quality of justice in the county.

"When you have animosity and competitiveness, the public ultimately suffers, because you have inefficient means to address prevalent problems in the community," Gartland said.

The March chase was just one of a series of recent incidents that reflect that animosity and competitiveness:

On June 10, troopers and deputies butted heads over who should get the credit for arresting a robbery suspect running from a bank with a bag of money in his hands. The deputies prevailed, but in the aftermath, the frustrated sheriff threatened to take away state police access to 911 emergency calls.

In February, state troopers walked off with a 38-year-old Waldorf man who had been handcuffed by a Charles County K-9 officer after allegedly stabbing two security guards at a local watering hole, according to several sheriff's deputies. The state police refused to hand over the prisoner even after a Charles County lieutenant arrived and demanded him back.

The same month, two state troopers joined sheriff's deputies in a chase of a suspected drunk driver that ended when the suspect rammed a sheriff's cruiser and wrecked his own vehicle against a tree. As the dazed suspect sat in his car, two state troopers approached, broke out two of the car windows, punched the suspect and sprayed him with pepper spray -- and then left, according to one of the sheriff's deputies who witnessed the incident.

There have been repeated instances of troopers failing to show up for court appearances -- including those before grand juries -- or failing to show up at court with essential evidence, especially seized drugs.

Under the 1994 agreement, state police in Charles County can still investigate crimes if specifically requested to by a member of the public, or if they witness a crime in progress or while making a traffic stop. Some county officials believe the remaining criminal investigative authority of the state police should be voided and the power ceded to the local sheriff's office.

"The county is growing," said State's Attorney Leonard C. Collins Jr. (D). "The sheriff's office is far bigger than it used to be and has more specialized units and staff."

Publicly, Sheriff Fred Davis (R), who spent 30 years as a state trooper, has not criticized his old agency, saying he believes relations with the state police are "better than ever."

Col. David B. Mitchell, superintendent of the Maryland State Police, agreed. "To my knowledge, we have a great working relationship," he said. "That's not to say troops don't get territorial now and then."

But police officials in Southern Maryland concede there are problems in Charles County. In April, Maj. Gary F. Cox, who was the southern region commander for the state police, issued a memo reminding troopers that criminal investigations are not their responsibility.

"We will only erode the public's confidence in us and tarnish our reputation as a department if we display inconsistency in our enforcement efforts with the sheriff's office," Cox wrote.

Lt. Michael Spaulding, the Waldorf barracks commander, said that in the February incident, his trooper didn't abscond with a prisoner but instead made a "legitimate arrest."

"The whole idea sounds ludicrous," Spaulding said. "Are these guys out here kidnapping the prisoners of another agency?"

The June tussle about the robbery suspect was a minor disagreement that was quickly resolved, Spaulding said, adding that talk of cutting off state police access to 911 radio calls would not be in the county's best interests.

Spaulding said he was unaware that either trooper had used excessive force in the second February incident, but he and Mitchell said they have launched an internal investigation of the matter in response to inquiries from The Washington Post. In the high-speed chase involving a car with stolen license plates, the troopers were spoken to about not backing off when requested but otherwise were not formally disciplined, Spaulding said.

The Maryland State Police are a $230 million agency with 23 barracks and 2,300 employees across the state whose troopers still serve as chief law enforcement officers in some smaller counties in Western Maryland and on the Eastern Shore. But in larger metropolitan counties such as Montgomery and Prince George's, the state police have focused their efforts solely on traffic enforcement, leaving criminal investigations to the locals.

State Police Lt. Col. Jesse Graybill concedes those remaining criminal investigation powers may need to be abandoned in growing Charles County. The county barracks "is transitioning into more -- and this is what our troopers hate -- highway patrol," Graybill said.

Trooper 1st Class Gary Carpenter, 38, who has spent his six years at the agency assigned to Waldorf, said: "All this stuff that has happened recently, it's unnecessary. It doesn't benefit anybody."

But Trooper 1st Class Danny Mabry, 29, who recently transferred to the Waldorf barracks from St. Mary's County because it is closer to his home in Indian Head, said he worries about not being treated as an equal by local deputies. "They're looking at us as a traffic police officer," Mabry said.

Spaulding confirmed that because of complaints by Collins and Rebecca Quinlan, clerk of the District Court, he has met with each in recent months to discuss the scheduling problems. Quinlan did not know how many times troopers had failed to show up for traffic court, but Spaulding said the incidents were isolated.

However, Collins confirmed that he met with Spaulding to discuss the "chronic problem" of troopers failing to appear at the courthouse for Circuit Court and grand jury proceedings. Over the past four years, he has complained repeatedly about no-show troopers to Spaulding and his predecessor, Lt. Miguel Dennis, to no avail, Collins said.

During two days of Charles County District Court proceedings this year, prosecution of several minor drug possession cases was disrupted because troopers were unable to open the evidence vault, sources said. At least two trials resulted in lighter plea bargains for the defendants because of the missing evidence.

"We are human, we do make mistakes, but the only thing we can do is address those mistakes when they happen," Spaulding said.

He said a new notification system will be put in place for court appearances as well as supervision of the drug vault. Troopers have had trouble unlocking the vault if the appropriate supervisor wasn't available, Spaulding said.

But Spaulding said that the troopers' failures to show up in court or with evidence were isolated events, not a pattern.

Mitchell agreed. "Is it wrong? Absolutely. Should our troopers be held accountable? Absolutely."

Spaulding said troopers at the barracks are performing well in their assigned areas. He said drunken-driving arrests are up 86 percent this year from the same period last year, and drug arrests are up 44 percent.

"We are making a positive impact on the community here. We feel we are saving lives and doing our jobs," Spaulding said.

Yet Judge Robert C. Nalley, the administrative judge for Charles County Circuit Court, said he has observed a "serious diminution in competence" in the state police since the late 1970s, when he was the state's attorney.

"I don't have any sense that it has improved a lot," Nalley said.

Collins said that he has asked the sheriff's office and state police to team up on the investigation and prosecution of vehicular manslaughter cases. He said that the sheriff indicated his deputies would comply but that the state police have been "unresponsive." State police officials say they think that idea is unrealistic.

Others have noticed different problems.

Circuit Court Judge Richard J. Clark became angry during a hearing on a vehicular manslaughter case last year when he learned that state police had delayed delivering the accident reconstruction report.

Clark ordered the prosecution to re-interview all state police witnesses in the case "because that is the only way I have learned that the state can find out exactly what these people are doing," Clark said. He also ordered the commander of the barracks and the state's attorney to meet with him about the problem.

"I have no problem talking to [the barracks commander] and telling him the problems that his office, his barrack, has created for [the state's attorney's] office in prosecuting cases that involve the Maryland State Police," Clark said, according to a transcript of the hearing. "He can complain to whoever he wants to complain to if he doesn't like what I have to say, I don't care."

CAPTION: Trooper Gary Carpenter talks to a motorist about not wearing his seat belt. In Charles County, troopers fear they are becoming little more than traffic cops.

CAPTION: Lt. Michael Spaulding, the Waldorf barracks commander for the Maryland State Police, said his troopers are performing well in their assigned areas.