Dieter Pfennig will remain in a prison cell for the rest of his life after he was sentenced to 35 years without parole for the murder of 10-year-old Adelaide schoolgirl Louise Bell in 1983.

Added to Pfennig's previous sentence for an unrelated murder, it makes a combined total of 60 years in prison without being eligible for parole.

Louise Bell was last seen alive in January 1983 when she went to bed at the family home in Hackham West in Adelaide's south.

Her body has never been found.

Her disappearance prompted a police search of then unprecedented proportions, with her disappearance becoming one of South Australia's most puzzling cold cases.

Pfennig, 68, was last month found guilty in the South Australian Supreme Court of her murder.

The 'most evil' of crimes

Justice Michael David told Pfennig his was "the most evil" of crimes and it was in no way "ameliorated by the passage of time".

"The shock and anxiety that your offence caused the South Australian community cannot be compared to the distress that must have been suffered by the parents and family of Louise Bell," he said.

"The effect of my sentence will be that you most certainly spend the rest of your days in jail."

Pfennig will not be eligible for parole until he is aged 103.

Dieter Pfennig was found guilty in November for Louise Bell's murder. ( Supplied: SAPOL )

Prosecutor Sandi McDonald had urged Justice David to hand down the toughest penalty possible.

"This man is entitled to no mercy," she said.

"Your honour should impose a non-parole period that would make it clear to the community, and to this man, that he has no expectation of any life outside of custody.

"It would be completely and utterly inappropriate to impose the mandatory minimum."

A woman who described herself as Louise Bell's "last teacher" said outside court she was "utterly relieved that justice had been done".

"He [Pfennig] got what he deserved and the judge was amazing," she said.

"It just shows that you won't get way with horrible things that are done."

Whereabouts of Louise's body remains unknown

Ms McDonald said police had also made two unsuccessful attempts to find out the location of Louise Bell's body since the Pfennig verdict last month.

Louise Bell's last teacher said she was relieved that justice had been done. ( ABC News )

But Pfennig's lawyer Grant Algie told the court that his client could not advise where her body was buried because he maintains he is not guilty of the offence.

"He has instructed us to advise your honour that if he did know where the body was he would tell you," he said.

Mr Algie had asked Justice David to hand down the minimum non-parole period of 20 years.

Pfennig is already serving a life sentence with a non-parole period of 38 years — later reduced to 25 years due to a sentencing legislation change in SA — for murdering Murray Bridge boy Michael Black in 1989 and later abducting and raping a 13-year-old boy.

Another man, Raymond John Geesing, was initially tried and convicted of Louise Bell's murder but that conviction was quashed on appeal in 1985.

Pfennig was arrested and charged with the murder in 2013 after advances in DNA technology led to a breakthrough during a review of the cold case.

Justice David told Pfennig during sentencing that he was not punishing him for his previous crimes against Michael Black and the 13-year-old boy.

"You've already been punished for those," he said.

"Also, I'm not punishing you for not accepting my invitation to tell the authorities the whereabouts of the bodies of Louise Bell and Michael Black."