A teenager was out on bail for drug-related offences when he bashed and robbed a woman, causing multiple facial fractures.

The 53-year-old woman was so shaken by the attack last October that she had to undergo psychotherapy sessions.

Her attacker, Rishi Christopher, who turned 20 last December, was yesterday sentenced to at least a year in reformative training. This means he will be sent to a reformative training centre, where he will follow a strict regimen that includes foot drills and counselling.

Rishi pleaded guilty on April 9 to committing robbery with hurt. He also admitted to one count each of theft, criminal breach of trust as well as drug possession and consumption. The victim cannot be named due to a gag order to protect her identity.

Police first arrested Rishi during a spot check in Toa Payoh on Sept 20 last year and his urine sample was found to contain traces of a synthetic cannabinoid.

A brown substance in his possession contained a similar drug. He was released on bail - only to commit further offences.

On Oct 17 last year, he made off with an $850 e-scooter from a Yishun shop after telling the store owner that he wanted to take it out for a test ride. The next morning, he stole items of clothing and a pair of shoes, worth more than $120, from a shop at Waterway Point mall in Punggol.

He was sitting at the void deck of a Punggol Way block of flats about three hours later when he spotted the woman. He followed her into a lift, got out with her at a higher floor and punched her face, causing the woman to drop her keys and cellphone. He then choked her and rained punches on her face.

Deputy Public Prosecutor Rebecca Wong told District Judge Eddy Tham: "The victim fell to her knees, screaming in pain. The accused continued to punch (her) while pulling on her handbag and telling her to let go. The victim refused."

The woman then grabbed Rishi's groin and squeezed it hard, forcing him to release his grip. She also tried to hit him with her umbrella but he flung it aside.

"The accused then tried to snatch the victim's handbag but to no avail... The victim held on to her bag and tried to crawl towards her umbrella. The accused kicked the victim away from him, grabbed her keys off the floor and fled the scene," the DPP added.

A resident who heard the commotion alerted the police. The injured woman was found slumped against a wall at the lift lobby. She was hospitalised for five days and given 27 days of medical leave. Police arrested Rishi in Yishun about four hours after the robbery.