A teenager who stabbed two taxi drivers in Sydney's west during a 24-hour spree in March 2024 was sentenced to four years' jail on Friday after telling the court he was suffering withdrawal from a drug he believed was fentanyl-laced vape liquid.

Hattam Assaad, 19, pleaded guilty in Parramatta District Court to aggravated robbery, inflicting actual bodily harm, and assault with intent to rob while armed with an offensive weapon causing wound or grievous bodily harm. Judge Phillip Mahony described the 20-centimetre knife used as capable of causing "serious injury" and sentenced Assaad to a term that will make him eligible for parole on Aug. 2, 2026, backdated to his first day in custody.

Court documents and prosecuting submissions outline two separate incidents. On March 28, 2024, police say Assaad got into a taxi at South Granville, produced the knife, pressed it to the driver's shoulder and demanded $500 after becoming angry at what he said was a higher-than-expected fare. The driver activated a duress alarm and parked at a Speedway petrol station at Guildford; Assaad fled, taking the taxi's dashcam.

The following day, police allege, Assaad entered a second taxi in Guildford and demanded $600, threatening the driver and seizing the man's mobile phone. The driver, 42, was stabbed multiple times in the hand and arm and later underwent surgery. He was treated on Aug. 31, 2024, the same day police arrested Assaad.

Assaad told officers he had used illicit substances in the 48 hours before the attacks and described heavy opioid use. The court heard that he had first been introduced to a nicotine vape liquid at about 17 and had been told it contained cannabis. He later discovered the product had been spiked with a synthetic opioid that he now believes was fentanyl, and told the court he was experiencing withdrawal and seeking money to buy more "vape liquid." He also said he had a switchblade and had been carrying it for protection after a gun was allegedly put to his head months earlier.

In a written apology read to the court, Assaad said, "Not one day goes by where I don't feel guilty or overwhelmed by what I've done. I apologise to everyone I've hurt and I will learn from this big mistake I've made." Defence counsel told the court Assaad was the eldest of eight children and suffering from post-traumatic stress disorder and unresolved trauma, which the judge said had contributed to his drug use.

Victim impact statements filed in court described ongoing trauma, physical pain, emotional distress and increased anxiety among the drivers. Prosecutors argued the knife attacks and thefts caused significant harm and warranted a custodial sentence.

Judge Mahony imposed a custodial sentence of four years and set the non-parole period to reflect time already served before sentencing. Under the sentence, Assaad will be eligible to seek parole on Aug. 2, 2026.

The case highlights concerns in Australia about illicit substances being sold in vaping products and the increasing presence of potent synthetic opioids in the illicit market. Authorities have repeatedly warned that unsuspecting users can be exposed to highly dangerous compounds when products are adulterated.

Police in western Sydney investigated the incidents as part of their response to an assault and robbery series in the area, and investigators said the arrests followed inquiries that linked the March attacks to Assaad. Court records show he pleaded guilty to the charges against him, avoiding a contested trial.

Sentencing remarks and the victim statements underscore the lasting effects on those attacked, while defence submissions and the offender's account pointed to addiction and trauma as contributory factors. The Parramatta District Court will consider reports and rehabilitation prospects should parole be sought when Assaad becomes eligible next year.