Melanie Lyn Slate was born on October 8, 1972, in Ridgewood, New Jersey. She grew up in both Ridgewood and Middletown Township. During her childhood, she attended Middletown High School South. After finishing high school, she enrolled at Rutgers University. At Rutgers, she studied both math and psychology, and she graduated in 1994.

After completing her degree, Melanie pursued a career in nursing. She attended the Charles E. Gregory School of Nursing, which is now known as Raritan Bay Medical Center. She graduated in 1997, earning her nursing diploma and finishing second in her class.

In 1999, Melanie married William T. McGuire, a United States Navy veteran. Together, they had two sons. At the time of their marriage, Melanie was working as a nurse, while Bill was a computer programmer. They lived in Woodbridge Township, New Jersey, and planned to move to a larger home in Warren County.

Melanie Lyn McGuire was involved in a tragic murder case that received notable media attention. On April 28, 2004, Melanie’s husband, William "Bill" McGuire, was killed. The prosecution argued that Melanie drugged her husband, shot him, and dismembered his body. The remains were later found in a three-piece suitcase set in Chesapeake Bay.

The investigation began on May 5, 2004, when fishermen discovered the first suitcase, which contained human legs. A second suitcase was found on May 11. This larger suitcase held a head and torso. The head had one bullet wound while the torso had two bullet wounds. The third suitcase, containing arms, was found on May 16.

Authorities identified Bill McGuire as the victim through a facial reconstruction. Melanie then became the prime suspect. Evidence collected during the investigation pointed to her guilt. On April 26, 2004, she purchased a .38 caliber handgun, which was the same type of gun used to kill her husband. Melanie also had a receipt that suggested a purchase of wadcutter bullets, which matched the ammunition used in the murder.

Further investigation revealed that Bill’s car was towed from a motel in Atlantic City shortly after the murder. Police discovered security footage showing the car being moved around the same time. Melanie claimed she moved the car as a prank, even though she had recently applied for a protection order from Bill.

Investigators found that plastic bags used to hold Bill’s body parts matched those used for his clothing, which Melanie had given away. A medical-grade towel found with Bill's remains was linked to Melanie's workplace, as she had used similar towels when moving her furniture. There were also green fibers found on one of the bullets that investigators theorized could have come from a couch owned by the McGuires.

On June 2, 2005, more than a year after the murder, Melanie was taken into custody. She was charged with first-degree murder and released on bail. Over the following months, she faced additional charges, and her bail was raised multiple times.

Melanie's trial began on March 5, 2007. The prosecution argued that she wanted to start a new life with her lover. Despite her claims of innocence, on April 23, 2007, the jury found her guilty of first-degree murder, perjury, desecration of human remains, and possession of a weapon for an unlawful purpose. She was sentenced to life in prison on July 19, 2007.

Melanie's conviction was affirmed by the appeals court in 2011, and her bid for a new trial was eventually denied. She is serving her sentence at the Edna Mahan Correctional Facility for Women in Clinton, New Jersey.