A smirking killer grinned his way into prison yesterday after being sentenced to 25 years to life for murdering a radio newsman.

John Katehis, convicted last month for stabbing George Weber 49 times during a Craigslist hookup, apologized to Weber’s family for the 2009 murder.

“For the death of George Weber, I’m sorry,” Katehis said. “For his family, I wish you the best. I regret it.”

The creepy teen — who grinned when he was convicted — smiled at his dad as he was led out of the courtroom.

Katehis went to Weber’s Cobble Hill, Brooklyn, apartment after Katehis agreed to perform oral sex on Weber, 47, for $60.

Lawyer Ron Kuby, who was a colleague of Weber’s at WABC, said the long sentence was “not only justified, but mandated.”

“No one does what he did at the age of 16 and gets better,” Kuby said. “Society needs to be protected from John Katehis.”