By Kathleen Brady Shea, Managing Editor, The Times

Stephen Shappell will spend 40 to 80 years in prison for the 2010 homicide of his boss, who was also his ex-lover’s husband.

He believed her when she said the only obstacle to their lifelong happiness was her husband. And even after Stephen Shappell sat behind bars because he carried out Morgan M. Mengel’s murderous plot, he was buoyed by the report that she had delivered his twins in prison.

None of it was true, Shappell, 24, later learned from police: The birth announcement was a ruse to get Shappell to take the fall for his former lover, who loved no one but herself, prosecutors said.

Last week, Shappell was scheduled to provide those details to a jury, but the trial did not happen.  Mengel, 37, pleaded guilty to the first-degree murder of her spouse, Kevin Mengel Jr., the 33-year-old father of their three children, a conviction that carries a mandatory life sentence without the possibility of parole.

On Monday, Chester County Senior Judge Thomas G. Gavin sentenced Shappell to a 40- to 80-year prison term for his pivotal role in the crime. Although the judge imposed the negotiated penalty without comment, he first heard emotional testimony from a half-dozen people, including the victim’s parents, brother and sister.

All of them expressed outrage that Shappell, an employee of Kevin Mengel’s landscaping company, committed the murder and then moved right into Kevin Mengel Jr.’s apartment.

Kathleen Barton, the victim’s mother, said her son had been trying to help and support Shappell, mindful that Shappell had lost his father to suicide as a teen. “He had such great plans for you,” Barton said to Shappell. “Now Kevin’s three children have no father.”

Kevin Mengel Sr. said he felt some sympathy for Shappell that quickly dissipated when he focused on Shappell’s disgusting behavior. After fatally bludgeoning his son, Shappell left the body for several days in an unused garage at the landscaping business while he slept in his son’s bed. But Kevin Mengel Sr. acknowledged that Shappell was a pawn. “You are just a stupid kid lured by lust into the evil web of a black widow named Morgan,” he said.

Unlike his co-defendant, Shappell asked to face the more than a dozen members of the Mengel family who attended the sentencing as he apologized.  Shappell, who was represented by David P. Clark, had no supporters in the courtroom, not even his mother, who has sometimes attended proceedings.

Shappell said he understood that his words meant little and could not undo the pain he caused. He said he hoped his “heartfelt remorse” would “help in some small way to ease some of the anger. … I’ll never forgive myself,” he said, visibly distraught. “I should never be forgiven.”

Chief Deputy District Attorney Patrick Carmody acknowledged the rarity of a plea agreement with a confessed killer, but he believed the circumstances warranted it.  He pointed out that Morgan Mengel  “picked and groomed” Shappell, preying on his weaknesses. “He held the shovel, but Morgan held the strings,” Carmody said, adding that Shappell expressed remorse and accepted responsibility early in the prosecution.

It wasn’t until last week that Morgan Mengel admitted that she goaded Shappell into killing her husband on June 17, 2010, at MKB Landscaping, the West Goshen Township business the couple ran.

She said she added toxic liquid nicotine to her husband’s favorite lemon Snapple and then texted Shappell to make sure it was being consumed. When it did not take immediate effect, Shappell struck Kevin Mengel with a shovel. When the shovel snapped, he grabbed another, and when it broke, he reached for a third one. Morgan Mengel arrived to clean up the scene and Shappell later buried the body behind his alma mater, Marple Newtown High School.

Kevin Mengel’s relatives became concerned when he uncharacteristically missed a Father’s Day outing. Then, relatives began receiving texts from his phone that did not sound like him. The author was Morgan Mengel, who was trying to persuade them that Kevin Mengel had left and needed some time alone. The family didn’t buy it.

On the night of June 24, 2010, Kevin’s brother, Chris Mengel, and some friends kept watch near the Mengels’ apartment. The next morning, they saw Shappell carrying items from the residence and loading them into an MKB landscaping truck. When Morgan Mengel jumped into the truck, Chris Mengel called police and followed the vehicle to the Mengels’ nearby business. Minutes later, as an officer questioned Morgan Mengel about the packed vehicle, Shappell panicked and took off but was later apprehended in Colorado.

Once both defendants were imprisoned, Morgan Mengel tried to use Shappell’s interest in having a family to her advantage. She lied that she was pregnant with his twins in prison, and even sent him a bogus birth announcement with names and weights, hoping to persuade him to take the rap so she could raise their children.

Carmody said he was present when police told Shappell the truth, news that clearly stunned and devastated him.