Christopher Jeffrey-Shaw, of Lakeside, Beckenham, south-east London, was found guilty at Guildford Crown Court of the manslaughter of German national and University of Brighton student Janet Muller, but cleared of the alternative charge of her murder.
The body of the 21-year-old, who had been beaten, was found in the boot of a burnt-out Volkswagen Jetta, which the defendant had dumped in a road by Ifield Golf Club in Crawley, West Sussex, on March 13 last year.
Jeffrey-Shaw, who has previous convictions for blackmail and harassment, admitted setting the car alight, but denied murder.
Philip Bennetts QC, prosecuting, told the trial that the defendant said he had been ordered at gunpoint by drug dealers to burn the car which they had taken to use in a botched robbery in which two people had been shot, and that he had not known Ms Muller was in the boot when he set alight to it.
Sentencing Jeffrey-Shaw, the judge, Mr Justice Jeremy Stuart-Smith, said that he rejected the defendant’s account of the robbery and ruled that he had witnessed her being put in the car.
He added: “I cannot find, on the basis of the jury’s verdict, he was responsible for the head injuries, but he knew she was in the boot.”
Mr Justice Stuart-Smith told the defendant: “The only difference between you and a murderer is an extremely thin line.”
He added: “Christopher Jeffrey-Shaw, the jury has convicted you of manslaughter on overwhelming evidence.
“What you did was deeply shocking and callous beyond belief and at every stage since you set fire to the car in which she died, you have lied and lied in your attempt to evade all responsibility for what you did.
“But you are responsible for killing a young woman who did you no wrong.
“On the jury’s verdict, the only reason you are not guilty of murder is because you did not have the human decency to check if the person in the boot of your car was dead or alive.”
He added: “To burn someone to death is a particularly vile way of killing someone.”
The judge said that the victim’s mother “could not stand to have her daughter cremated because she has already endured one fire”.
He added: “You deprived Miss Muller’s parents of their daughter and her twin sister of her other half in a most devastating way.
“When her sister says half of her has gone and she will never celebrate her birthday again, everyone in this court, except you maybe, can understand a little of what she can be experiencing.”
Bernard Tetlow QC, defending, said of his client: “Someone who is a loving and devoted father has gone considerably off the rails in recent times having recently become heavily dependent on drugs.”
Mr Bennetts said Ms Muller had been experiencing mental health problems and had been admitted to Mill View Hospital in Hove, East Sussex, but went missing on the evening of March 12 and she was last seen approaching an unidentified car later that night.
He told the court that phone records and CCTV footage showed that the defendant’s phone and his car were in the Brighton area on the evening that Ms Muller disappeared.
Denying her murder, Jeffrey-Shaw told officers: “I am not getting done for something I haven’t done. The whole thing is a nightmare I haven’t woken up from.”
Detective Superintendent Karen Mizzi, of the Surrey and Sussex major crime squad, said after the trial: “This was a horrific attack on a very vulnerable young woman who had her whole life ahead of her.”
Ms Muller’s family said in a statement: “We are not happy that the verdict is manslaughter, not murder.
“We are glad that the man responsible for Janet’s death will not walk free but nothing can erase the loss of Janet.”
A University of Brighton spokesman said: “Janet was a bright, sparky and witty student.”
Ms Muller was buried in Berlin last May.