About once a year, a chase involving local police officers results in someone being seriously injured or killed.

Sometimes it's the fleeing suspect who's injured or killed; sometimes it's an innocent bystander.Last Monday, it was an innocent bystander. When Boyd Day, 69, Fillmore, started to turn left from East Bay Boulevard onto south University Avenue about 6 p.m., he had no idea his life was about to end. But then a car fleeing from Utah Highway Patrol troopers struck Day's car at 70 mph.

Whenever someone dies as a result of a chase, the same question always arises: Was the chase justified?

The question is one police face constantly, and it's one they hope to answer to the satisfaction of the people they're paid to protect.

"Even if the officer does nothing wrong, it's hard to tell a family that their child has been killed," Provo Police Capt. Mike Mock said.

Because of the increasing number of high-speed chases ending in serious accidents, police have changed their philosophy over the past few years. Ten years ago, police pretty much would chase anyone who fled - but not anymore.

"Our feeling is that it has to be pretty serious for us to pursue," Mock said.

Police agencies now have guidelines that officers use to determine when to pursue a suspect and when to terminate a chase. For most agencies they are similar. Determining factors might be:

- The severity of the offense.

- The nature of the suspect.

- The time of day.

- The area and street involved.

For example, a chase is more likely on a highway than a city street because of the lack of traffic congestion, traffic signals and pedestrians. Someone suspected of robbing a bank is more likely to be pursued than someone with an expired registration. It is up to each officer to decide when to begin or terminate a chase.

"Every officer is instructed that if a pursuit does not justify the risk, then it's their responsibility to terminate it," said Orem Police Lt. Mike Fenton, patrol commander. "They are trained to understand the risks involved and to respect the potential danger of a high-speed chase."

Also, patrol supervisors monitor every chase over the radio and have the authority to terminate a chase if it becomes dangerous.

"I don't think people realize the number of chases that are terminated but never end up in the newspaper. It happens all the time," Fenton said.

However, terminating a chase does not always alleviate the danger. Usually once an officer slows down the person being chased does not. Police find this especially true in chases involving scared juveniles.

"They are going to keep going just as fast as they can to get as much distance as possible between them and the police," Fenton said.

The sheriff's office is one of a few Utah County agencies that use a hollow spike strip to stop fleeing vehicles. The rubber matted strip is placed across one lane of traffic, and when run over by a vehicle the hollow pins deflate the tires.

The strips almost played a part last week. Deputy sheriffs were positioned on U-214 ready to use the hollow spike strips. But after taking the north Spanish Fork exit that leads to U-214, the fleeing car returned to I-15.

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The victims:

Utah County deaths resulting from chases:

-March 18, 1991 - Boyd Day, 69, Fillmore; killed on south University Avenue in Provo when struck by car fleeing from Utah Highway Patrol troopers.

-July 12, 1990 - Dennis W. Peterson, 36, Payson; killed when car fleeing from Springville police plunges into Salem,Canal near Lake Shore.

-March 28, 1987 - Chad Michael Weaver, 19, Spokane, Wash; killed in Provo when his car was hit by a car being chased by Provo police.