WHEN A CELEBRITY HAIRSTYLIST IS KILLED POOLSIDE, INVESTIGATORS LOOK AT HIS WIFE - WAS HER ALLEGED AFFAIR WITH HER RACQUETBALL COACH A MOTIVE FOR MURDER?

Convicted Killer and Alleged Lover Robert Baker Exclusively Tells "48 Hours" the Wife Had Nothing to Do with It, in "The Monica Sementilli Affair"

Well-known beauty executive Fabio Sementilli was sitting by his swimming pool when he was brutally stabbed to death. His body was discovered by his then 16-year-old daughter Isabella on Jan. 23, 2017. Prosecutors say his wife, Monica Sementilli, was secretly having an affair with racquetball instructor Robert Baker. Baker defends Monica Sementilli on 48 HOURS: "The Monica Sementilli Affair," to be broadcast Saturday, March 9 (10:00-11:00 PM, ET/PT) on the CBS Television Network, and streaming on Paramount+.

"Monica did not know. She didn't know s***," Baker tells 48 HOURS. "If she did find out, I would have been in [jail] a lot sooner."

At first, police thought Fabio was a victim of a robbery gone wrong. Police had one good clue to go on: a neighbor's security camera caught two hooded figures near the house and later taking off in Fabio's black Porsche.

But investigators noticed not much else was taken, even Fabio Sementilli's $8,000 Rolex was left behind. The crime seemed to go unsolved for months, but secretly detectives had a lead. They had discovered DNA at the bloody scene. DNA that didn't belong to the victim. That DNA led them to Baker.

Investigators say Baker was having an affair with Fabio's wife. In court filings, prosecutors say Monica Sementilli had shared the password for her home security system with Baker. She maintains she's innocent and says she had nothing to do with her husband's murder.

"According to the prosecution, these two were plotting and planning to kill Fabio so they could live their life together," CBS News consultant Mary Fulginiti tells 48 HOURS.

According to police testimony, the day she and Baker were arrested in 2017, Monica Sementilli was recorded saying, "Somebody must have talked."

Both she and Baker pleaded not guilty, but in July 2023, Baker changed his plea to no contest and was sentenced to life without parole.

48 HOURS went to visit Baker in jail. He told us Monica had nothing to do with the murder and she never knew he was the killer.

Still, most of Fabio Sementilli's family have turned against Monica Sementilli, though the daughters she shared with her husband are supporting her. She is set to go on trial in April 2024.

Judy Tygard is the executive producer of 48 HOURS, which is broadcast Saturdays at 10:00 PM, ET/PT on CBS, and streams anytime on Paramount+. You can also watch 48 HOURS on the CBS News Streaming Network Wednesdays at 8:00 PM, ET. 48 HOURS is also available on CBSNews.com, Fave TV, Pop TV, Pluto US, Pluto UK, Pluto Nordics, Pluto Canada and Pluto South Africa. Download the CBS News app on your phone or connected TV. Follow 48 HOURS on X, Facebook and Instagram. Listen to podcasts at CBS Audio.