A "raving and violent marauder" will spend an extra four months behind bars for importing drugs from Europe before he murdered a beloved Canberra grandfather.
The offender, who cannot be named because he was underage at the time in question, used the dark web to import 86 MDMA tablets that were addressed to him at his ACT home.
Authorities intercepted the parcels when they arrived in Australia from Belgium and the Netherlands in early 2019.
It was in March that year that the offender, then aged 17, stomped on the head of Richard Cater, 82, in suburban Gungahlin during a drug-induced psychosis.
Justice Michael Elkaim previously said the teenager had "descended into a raving and violent marauder" while "tripping" on cheap LSD.
The offender has been in custody ever since his arrest on the night of Mr Cater's murder, when he also seriously assaulted two of the elderly man's friends as they returned to the 82-year-old's home from a dinner outing.
The killer, now aged 20, was sentenced last year to 11 years and nine months in jail for the murder and the associated attacks.
He only has to serve four-and-a-half years of that term in full-time custody, however, meaning he was due to be released from prison in September 2023.
However, in March, he pleaded guilty to charges of importing a marketable quantity of a border-controlled drug and possessing a prohibited weapon without authorisation.
Sentencing remarks, published on Thursday, show he fronted the ACT Supreme Court late last month to be sentenced by Acting Justice Stephen Norrish for those offences.
Acting Justice Norrish said the offender had imported 56 MDMA tablets on one occasion and 30 on another, demonstrating "a considerable lack of sophistication" by using his own name and address to order them.
He accepted the submission of the offender's lawyer, Sam McLaughlin, who said the young man had been a "user-dealer" who took MDMA every two or three days.
The judge found the offender had been "well on notice" about the consequences of being involved in drug importations despite his youth, given his electronic devices had contained "police media images of detained people".
Acting Justice Norrish also described it as "disturbing" that a person so young had been able to negotiate the "pernicious" dark web to obtain illicit drugs.
The judge said the offender had been living at home with his father when he imported the drugs and committed the "horrendous" murder.
The charge of possessing a prohibited weapon arose from police finding two knuckledusters during a search of the offender's home after Mr Cater's killing.
In sentencing, Acting Justice Norrish said the offender had completed Year 12 whilst in custody and proposed to live with his father again upon his release.
The young man, now studying a course in horticulture, was said to have been "a dedicated student" who had been a positive influence on others behind bars.
"He takes full responsibility for his offending," Acting Justice Norrish said.
"Whilst he, in the context of all the criminality for which he is responsible, be seen as a work in progress, there are certainly very positive signs which I accept and he should be given credit for the progress he has made."
The judge added that the youngster's risk of reoffending was considered low.
Acting Justice Norrish ultimately sentenced the 20-year-old to one year and eight months in jail for the drug importation and weapons offences.
He ordered that the sentence begin on the offender's previous release date and that it be suspended after four months, meaning the young man will now be freed from custody in January 2024.
