Beverly Coon was either a scorned lover willing to set her boyfriend afire in revenge, or a woman in love whose worst offense was trying to hide her relationship with a married school superintendent, according to starkly different opening statements yesterday in her trial on charges of arson and attempted murder.

Ms. Coon, 47, dabbed her eyes as a prosecutor told a jury of seven men and five women that she drugged her then-boyfriend, Ronald Grimm, one year ago, then set his bed afire after he passed out in a chair in his Monroeville apartment.

"We'll show you she had the opportunity and she had the motive to commit the crime," said Assistant District Attorney Thomas Pratt in an opening statement to jurors. The motive, say prosecutors, was that Dr. Grimm, then superintendent at the Bethel Park School District, wanted to end his relationship with Ms. Coon, at that time a member of the Baldwin-Whitehall School Board.

The pair met in 2003 at a school boards meeting in Hershey, and began an affair. According to prosecutors, Dr. Grimm had told Ms. Coon that he was planning to reunite with his estranged wife.

They say she drove to Dr. Grimm's apartment late Sept. 8, fed him drugged pastries, set his bed on fire, then watched as crews rushed to the scene in the wee hours of Sept. 9. She later attracted suspicion when she told a county detective she lived in the building, giving conflicting answers about why she was there.

Mr. Pratt told jurors he was going to present a circumstantial case -- but one in which the accumulated details, timing and evidence all pointed to Ms. Coon stalking, drugging and then attempting to kill Dr. Grimm.

"He's telling you this is a circumstantial case, but he's not giving you all the facts," countered defense lawyer Eric Fischer, who tore into the state's case, saying police failed to test the remaining pastries found in Dr. Grimm's refrigerator to see if they contained any drugs, did no tests on electrical appliances in the apartment to see if they were the source of the blaze, then waited until after the damaged apartment was being renovated to charge Ms. Coon one month later, making it impossible for the defense team to do an independent investigation.

Defense lawyers even questioned Dr. Grimm's account of breaking off his relationship with Ms. Coon, who was separated from her husband.

After telling Ms. Coon he was thinking of reuniting with his wife, "Mr. Grimm still sends her cards every week -- love, Ron." On Ms. Coon's birthday, "he sends her a dozen, premium red roses, delivered to her house. Love, Ron," Mr. Fischer said.

Ms. Coon had arrived at the scene of the fire, Mr. Fischer said, because she was returning to thank him for helping her figure out a problem with her daughter's computer. After witnessing the fire, he added, she traveled to Mercy Hospital, where she spoke with Dr. Grimm and asked him if there was anything he needed.

According to Mr. Fischer, Dr. Grimm told Ms. Coon he wanted his wallet and that she had returned to the apartment building to fetch it when she was stopped by police and questioned.

Mr. Fischer acknowledged that she lied to police by telling them she lived in the building and was waiting for firefighters to move emergency trucks that were blocking her car. She lied, he said, to cover up her affair with Dr. Grimm.

After the fire and arrest, Dr. Grimm resigned his post as superintendent in Bethel Park, and voters in the Baldwin-Whitehall district rejected Ms. Coon for a second term on the school board in last year's general election.

Yesterday's opening statements and early testimony in the courtroom of Common Pleas Judge Jeffrey Manning also raised questions about the fire alarm system inside the Monroe Village apartment building where the fire broke out. Investigators discovered that a power switch for the building's alarm system had been turned off.

Dr. Grimm, 61, sat in a hallway outside the courtroom, alongside his wife, Joyce. As did Ms. Coon, he declined to comment, but is expected to testify, possibly today.

Mr. Fischer and his co-counsel, Robert Leight, say they will present new evidence that will poke holes in the state's case against Ms. Coon.

"She's been wrongly accused of a crime. She's emotionally distraught. She looks forward to the jury absolving her of any involvement in this," Mr. Fischer said.