A man cut a teenager's throat in an unprovoked attack and then strolled into a supermarket to eat raspberries.
Colin Clarkson, 51, whispered "random murder" as he knifed the 19-year-old outside an Asda store in Grimsby in July.
He then calmly walked into the shop and sat on the floor eating berries while waiting for police to arrive.
Clarkson admitted attempted murder and possessing an offensive weapon and was jailed for 10 years and eight months.
Crown Prosecution Service lawyer Jeremy Evans said the victim was "very lucky to escape with his life" after the "brutal, random and completely unprovoked attack".
At Hull Crown Court, Clarkson, of Heneage Road, Grimsby, was also handed a five-year extended licence period.
Mr Evans said: "Clarkson suddenly slashed the victim's throat several times with a knife, leaving a number of gaping wounds, the largest of which was 10cm long.
"The wounds missed the carotid artery by only 5mm."
In a statement, the victim said Clarkson's attack had left him jumpy and nervous and "suffering with flashbacks".
"My whole life changed in seconds," he said.
"I have grown a beard to disguise the injury. That way I don't have to see it each time I look in the mirror or see a photograph.
"I have never caused him harm. I had never met him and he has stolen so much of my life."