An Alice Springs teenager with fetal alcohol spectrum disorder has been jailed for six months after breaking into the home of an 80-year-old pensioner and terrorising her with a boomerang, before stealing her bank card and car.

The NT Supreme Court heard Leroy Mills, 18, already had a rap sheet of nearly 40 offences and was out on bail when the incident occurred in the Central Australian town on January 24.

Mills broke into the victim’s unit at 5:40am and threatened her with the boomerang, telling her to be quiet and demanding money.

After being told by the pensioner she had no money, Mills took her bank card and demanded its pin number, which he wrote in pen on his forearm, the court heard.

He then stole the victim’s keys and took off in her car, driving to a number of service stations in Alice Springs and withdrawing $300 in cash from an ATM.

The victim contacted police after Mills left her property and officers soon found him filling up the stolen vehicle at the Coles Express truck stop on Dalgety Road in Braitling.

Mills fled when approached by the officers and was eventually apprehended near Dixon Road, where police found a fold-up knife with a seven-centimetre blade, cannabis and a pair of scissors in his pockets.

Justice Peter Barr said Mills had an extensive criminal history and had previously assaulted police officers and escaped from a youth detention centre before his latest offence.

“You recalled that the victim had told you that she was a pensioner and that she had no money … you recalled swearing at her and telling her to sit down and shut up,” Justice Barr said to Mills.

“You recounted that the victim looked scared and that she was crying.

“You did not want to cause her physical harm, but you wanted to intimidate her to get money and cigarettes.”

Justice Barr said Mills had been diagnosed with fetal alcohol spectrum disorder and sometimes struggled to understand “what is socially appropriate and the consequences of his actions”.

“Nevertheless, I have no doubt that at the time you offended, you were fully aware that what you were doing was socially inappropriate, and that your actions would inevitably lead you once more into the criminal justice system,” he said.

Justice Barr sentenced Mills to 18 months behind bars, with a non-parole period of six months.