In his closing argument on Monday, Mr. Bo unveiled more explosive elements surrounding his family, and essentially argued that the saga came down to crimes of passion. He said Wang Lijun, the former police chief of Chongqing, which Mr. Bo governed until his downfall in March 2012, had a final falling out with Mr. Bo and fled to a nearby American consulate in large part because of tensions that boiled over from his secret affair with Mr. Bo’s wife, Gu Kailai. Mr. Wang had told Ms. Gu that he was in love with her, and that outraged Mr. Bo, he said. His wife and the police chief had been close for years, he said, ever since Mr. Wang came to Chongqing to investigate Ms. Gu’s suspicions that she had been poisoned.

“Because he and Gu Kailai were stuck together as if by glue, Gu Kailai took him at his word, and Wang Lijun infiltrated my household because of his association with Gu Kailai,” Mr. Bo said Monday. “So now such a serious thing has occurred.”

He added: “The two had an extremely special relationship, and I was so sick of it.”

Mr. Bo said Mr. Wang harbored an enduring “secret love” for Ms. Gu, and that “his emotions were twisted; he could not free himself.” Mr. Wang expressed his feelings in one or more letters to Ms. Gu, Mr. Bo said. One day, Mr. Wang told her of his love and slapped himself eight times in front of her.

According to Mr. Bo, Ms. Gu said: “You’re abnormal.”

“I used to be abnormal, but now I’m normal,” Mr. Wang said, according to Mr. Bo.

Then Mr. Bo suddenly walked into the room, he said, and took the letter or letters away. “He knew my character,” Mr. Bo said. “He harmed my family. He harmed my basic feelings. That’s the true reason for his defection.”

The sequence of events was not clear, but Ms. Gu, according to Mr. Bo, at one point entered a room of Mr. Wang’s in Chongqing and stuck 60 or 70 notes on the walls that warned Mr. Wang to be careful. At another point, Ms. Gu brought Mr. Wang’s shoes to the Bo family home, and Mr. Bo asked a close aide to take them away, he said.