Thomas J. Capano, a wealthy lawyer and power broker in Delaware politics, was found guilty today of murdering one of his many mistresses, the scheduling secretary of Gov. Thomas R. Carper. After a 12-week trial and three days of deliberations, a New Castle County jury agreed with prosecutors that Capano, 49, killed Anne Marie Fahey, 30, in his home in June 1996 and sought to cover up the crime by tossing her body into the Atlantic Ocean. Fahey's body has not been found. Capano said nothing and remained expressionless when the jury foreman pronounced him guilty of first-degree murder. The approximately 175 people packed into the courtroom were also silent, but the crowd that had gathered just outside the locked doors erupted into shouts and applause. Fahey's relatives said they were relieved at the outcome. "It's been 934 days since Anne Marie took her last breath," said Robert Fahey, one of her four brothers. "Today, we finally found the truth, for which we're very thankful." David C. Weiss, the Fahey family's attorney, added: "No matter where you come from, no matter how privileged your background, justice applies to everybody." The jury must now recommend whether Capano should be given the death penalty or sentenced to life in prison without parole. Under Delaware law, the final decision rests with Judge William Swain Lee. The penalty phase of the trial is scheduled to begin Wednesday and is expected to last about a week. In an echo of Washington scandals involving the sexual relations of prominent people, the sensational murder case has transfixed the state of Delaware and the surrounding region since June 1996, when Fahey was reported missing by her family. The subsequent investigation revealed more than the affair between Fahey and Capano, who is married and the father of four. It also spilled secret after secret about the tawdry activities of many leading figures in Wilmington's close-knit political circles. More than a few careers and reputations were ruined by the disclosures. "Tom Capano put a lot of people through a lot of distress, suffering and pain," said Colm Connolly, one of the prosecutors. "He will have to pay a price for his conduct." Members of Capano's family, which is well-known in Delaware for its extensive business holdings, declined to comment as they left the courthouse. Capano's defense team also had little to say. "We're not happy," said Joseph S. Oteri, one of his four attorneys. "The four of us broke our backs on this. The jury was a serious jury. They've spoken, and we're bound by that." Pressed for Capano's reaction, Oteri said his client didn't utter a word afterward. "He fully believed he was going to be acquitted this morning," Oteri said. The verdict was full of harsh ironies for Capano, a onetime state prosecutor who served as legal counsel to former governor Michael N. Castle (R) and chief of staff to former mayor Daniel Frawley (D). Although Capano often bragged about his potent political connections, his fate was sealed by an aggressive criminal investigation that drew the personal involvement of Carper (D) and President Clinton, who offered the services of the FBI. And although Capano preached the virtues of family loyalty, the most damning witnesses were two of his brothers, who testified that they helped him destroy virtually all of the physical evidence of Fahey's death. "His career has been shattered, his reputation has been shattered and his family has been shattered," said Ferris Wharton, another prosecutor. "And you have to ask yourself, for what?" The motive, prosecutors argued, was jealousy. After being involved with Capano for more than two years, Fahey wanted to dump him for another man, a young bank executive with whom her boss, the governor, had fixed her up, prosecutors said. Capano, however, didn't want to let go. He showered her with expensive gifts, but he also bullied her and preyed on her insecurities, according to testimony. "He's {expletive} stalking me," she told a friend one month before she died. Although authorities conceded they didn't know exactly what happened the night Fahey died, they theorized that she had agreed to meet Capano for dinner at a Philadelphia bistro so she could break off her relationship with him. Instead, they said, he took her back to his house in a fashionable section of Wilmington and killed her. Failing to find Fahey's body or a murder weapon, prosecutors had to rely heavily on circumstantial evidence, including passages from Fahey's diary and e-mail messages between Fahey and Capano that detailed their on-again, off-again relationship. As part of a plea agreement, Capano's youngest brother, Gerard, told authorities that he and Thomas had used a cooler to dispose of a body. Gerard Capano said they took his fishing boat 60 miles off the New Jersey coast and tossed the ice chest and corpse into the sea. When the cooler just floated on the waves, Gerard said, he unsuccessfully tried to sink it with a blast from a gun he used for shark hunting. Prosecutors then stumbled across a single, crucial piece of physical evidence. More than a year after Fahey vanished, some Delaware fishermen told investigators they had found a large white cooler bobbing in the ocean. The cooler, which was marked by a bullet hole, was Fahey's coffin, Gerard Capano said. The discovery changed the course of the case. After repeatedly denying that he knew anything about Fahey's disappearance, Capano changed his story at the trial's outset. In testimony, he said that he watched Fahey die and that he got rid of the body. But he testified that he did not kill her. Instead, he blamed another of his mistresses, a private school administrator named Deborah MacIntyre, for Fahey's death. According to Capano, MacIntyre burst into his house one night and discovered him snuggling on the sofa with Fahey. He said MacIntyre was distraught, threatened to commit suicide and waved a gun around. When he tried to grab her arm, Capano said, the gun fired accidentally, killing Fahey with a single shot to the head. MacIntyre, who had been involved romantically with Capano for 15 years, denied his account. Prosecutors ridiculed it. "It doesn't make sense that a man with all those connections would try a coverup," Connolly said in his closing argument. "It defies common sense. It isn't credible." The jury didn't buy it, either. Capano's own demeanor on the witness stand may have been one reason. When his own attorney asked him how many women he was having affairs with while he was dating Fahey, Capano replied cavalierly that there were too many to count. "Eight or nine," he shrugged. He also didn't gain much sympathy when he described his sexual habits in X-rated detail. Jurors heard how he enjoyed porn movies, voyeurism and trysts in parking lots and cheap motels, not to mention a menage a trois with MacIntyre and Delaware's chief deputy attorney general. And if there were doubts that Capano had a vicious temper, they vanished during cross-examination. During one tense line of questioning, Capano shouted at Connolly: "You heartless, gutless, soulless, disgrace of a human being!" Capano still faces a number of legal problems in addition to his sentencing. While in prison awaiting trial, he was charged with attempting to hire a hit man to kill MacIntyre and his own brother Gerard. He also is being sued by the Fahey family for Fahey's wrongful death. Asked whether they preferred that Capano be sentenced to life or death, Fahey's siblings said they were content to let the court choose. "In some ways, life in prison would be a crueler punishment," Robert Fahey said. "But it's really up to the jury and judge to decide." CAPTION: Onlookers outside the courthouse in Wilmington, Del., applaud the verdict against Thomas J. Capano. ec CAPTION: Thomas J. Capano, 49, right, was found guilty of killing his lover, Anne Marie Fahey, 30, left, in his home in 1996 and throwing her body into the ocean. ec