Lon A. Lewis, 29, was found guilty yesterday of first degree murder for conspiring to murder his wife Carol in a "You-kill-my-wife, I'll-kill-yours" deal with a fellow computer technician.

After deliberating for two hours, a Prince George's County jury also found Lewis guilty of second-degree murder for conspiring to kill his 4-month-old daughter, Heather.

Carol and Heather Lewis were found stabbed to death in the kitchen of their home at 4807 Raemore La., Bowie, on the night of Sept. 23.

Lewis stared straight ahead, holding his hands clasped in front of him, as foreman Patricia O'Boyle answered "guilty" when asked the verdict on each of seven charges.

He spoke briefly with his mother and father, who sat in the courtroom during the entire five-day trial, before being led away by marshal. HE will be sentenced on July 13.He could be sentenced to life imprisonment.

"Lon is relieve, he says it's all in the hands of the Almighty now and he's glad it's over," his mother, Lena J. Lewis, said.

Defense attorney Leslie Gladstone had argued during his one-hour closing statement that Lewis was, "morally guilty for not protecting his family as he should have, but not legally guilty as charged by the state." He labeled the verdict, "sentimental."

"The jury reacted to the violence and brutality of the murders," he said. "I think their verdict was quickly conceived in light of the evidence." He said he would appeal on all counts.

The verdict concluded a five-day trial that evolved into an emotional melodarma played out before packed courtrooms each day.

On Thursday, Lewis testified that he had considered the plot "a game."

Yesterday morning, under 90 minutes of cross-examination by prosecutor Joseph Sauerwein, Lewis broke down repeatedly as he had on Thursday.

Once, Sauerwein said that Lewis knew he was going to "receive something," (according to earlier testimony he sought freedom to live with another woman) by conspiring in the murders. Lewis, his voice choking, shouted back, "What am I going to receive. I'm going to go to prison for the rest of my life for it. That's a helluva thing to receive."

Later, clinical psychologist Dr. David Shapiro testified that testing he did on Lewis in November showed that he was "emotionally incapable of understanding what was going on. Intellectually he understood that what he was doing was wrong." Shapiro said, "but emotionally he never knew that this was a real murder being discussed until after the actual act."

In his closing statement Sauerwein-referred frequently to the written confession Lewis made to police on Oct. 7. Init he detailed the plot and his affair with a woman in San Antonio.

According to Lewis' statement and his testimony during the trial, Gene T. Meyer suggested to Lewis in April 1977 that he kill Lewis' wife so he could be free to be with the Texas woman. Meyer and Lewis were both in San Antonio in computer training sessions for their company, Data-Point Corp., at the time.

Later, Lewis testified, he and Meyer agreed to a "you-kill-my-wife-I'll-kill-yours" plot during meetings at Gene's on the Pike Tavern, 11608 Rockville Pike, Rockville. Meyer, who was convicted April 27 of slaying Lewis' wife and daughter, allegedly wanted his own wife killed in order to collect on an insurance policy.

Sauerwein argued that the combination of the months of planning and Lewis' telling Meyer the night before the murders to "do whatever's easiest," made the two men "joint senior-partners."

"This was no game to Lon Lewis," Sauerwein said. "If he wanted to be rid of his wife he just could have left her. But he wasn't man enough to do that.Or man enough to do anything else."

Gladstone began his summation by telling the jury that the case was "the most tragic I've ever dealt with in 10 years of practice."

"What makes it so tragic," he continued, "is that Lon Lewis loved his wife and daughter. Yet even today he cannot explain why he did not act to protect them. He'll live with that burden the rest of his life."

Gladstone then argued that the state's entire case was based on Lewis' confession and that the statement had been made involuntarily.

"To say after two days of polygragh tests and being accused over and over again of committing murder, when you didn't commit the act, that a statement given is given of free will is an absurdity," he said.

After O'Boyle's reading of the verdict, Gladstone asked for a polling of the jury and all 12 members, answered that they agreed.