Court. MHK's sentence, which has a minimum jail term of five years and three months, has sparked fierce debate in national security circles, including concerns about whether it will sufficiently deter suspected young jihadis being actively monitored by security agencies. However, defence lawyers are understood to believe the sentence was appropriate given the teen was 17 when he was arrested in May 2015. The case raises complex questions about dealing with teenage extremists through the criminal justice system, where judges must weigh up a person's age, level of remorse and prospects for rehabilitation against the seriousness of their offending. An increasing number of the 400 or so suspected Australian extremists under surveillance are teenagers. National security officials are concerned the sentence was too lenient and the case represented a "lost opportunity to send a strong message".

It is understood prosecutors are concerned the sentence was "manifestly inadequate" though it is believed Justice Lasry did not err in law in delivering the punishment on Wednesday. In October, the Director of Public Prosecutions appealed to increase the 10-year maximum sentence given to Melbourne teen Sevdet Besim, who was convicted of planning to kill a police officer during the 2015 Anzac Day commemorations. Justice Lasry said he sentenced MHK on the basis of what he would have done if police had not intervened. "Had you not been arrested you would have killed and injured innocent people," the judge said. The judge said it was a particularly difficult sentence because MHK was young and a first-time offender. Yet he said that three years in a youth justice centre would "fail to recognise the objective seriousness" of his crimes.

"Young people...must understand that despite their youth, significant punishment awaits [for such crimes]," the judge said. The judge recommended the Adult Parole Board not imprison the man with extremists and violent offenders. He also recommended that the teenager spend as much of his non-parole period as possible in a youth justice centre, and that he continue his rehabilitation. MHK, who has a Syrian background, had maintained a strong interest in the war in Syria. As he searched for information about the war and his faith, he began reading Islamist propaganda and became a IS supporter, the Supreme Court heard. The teenager also began chatting on Facebook to an older IS recruiter who has since died fighting in Syria. The recruiter encouraged MHK to launch a terror attack in Melbourne after he realised that he would not be able to join the war in Syria as he did not have a passport.

The recruiter sent him links to articles that gave detailed instructions on how to make improvised explosive devices using basic household materials. MHK pleaded guilty to partially constructing an improvised explosive device and accessing documents related to such devices in preparation for or planning of a terrorist act. In a previous hearing, MHK testified that he was "very embarrassed" and "ashamed" of his plans to build bombs in preparation for a terrorist attack. He also warned Australians aspiring to join Islamic State that doing so would lead only to them "wasting their life". The case has drawn attention from deradicalisation experts and senior police, amid evidence suggesting that intensive efforts to deradicalise the teenager appear to have worked. The man had frequent interaction with teachers at the Melbourne Juvenile Justice facility and an Islamic leader.

MHK cannot be named because he was first charged in the Children's Court.