A man with a "psychopathic personality disorder" has been jailed for life after killing a stranger by stabbing her in the neck with a broken bottle.
Miss Roberts' family said she was a "loving, caring person"
Gemma Roberts, 18, bled to death outside the Swan Hotel in Liversedge, West Yorkshire, in September last year.
Richard Hanson, 21, pleaded guilty to manslaughter on the grounds of diminished responsibility.
Medical experts said Hanson, of Stubley Farm Lane, Heckmondwike, had a psychopathic personality disorder.
The court heard that Hanson attacked Miss Roberts, who was a stranger to him, in a random incident in the street.
James Goss QC, prosecuting, said Hanson has been "behaving in an increasingly bizarre and aggressive way" in the days leading up to the attack.
Sentencing Hanson to life in jail, Judge Peter Collier told him: "Not only did you cut short her promising life but you have devastated her family who will struggle to come to terms with her death for many days to come.
"You are in my view, a very dangerous young man and the only sentence I can pass on you is a sentence of life imprisonment."
The judge set a minimum period in custody of two years and 320 days but warned Hanson he "may never be released" and said he would be subject to a licence for the rest of his life.
In a statement Miss Roberts's family said they had been left with a "massive hole in our lives" and they still could not believe she was gone.
Det Supt Andy Brennan, of West Yorkshire Police, said Miss Roberts had a chance encounter with Hanson who carried out an unprovoked attack.