Lee Mitchell, 31, had entered the shop at Letterkenny and tried to grab money from two cash registers.
When a shop assistant tried to stop him, he head-butted her and then punched her in the cheek.
The woman suffered a hairline fracture of her nose and also severe bruising.
Two local men came to her rescue and tried to intervene but Mitchell managed to run off but was arrested the next day.
Mitchell, of 3 Glencar Park, Letterkenny, was charged with both criminal damage and assault causing harm on February 11th last.
Mitchell had been remanded in custody to appear at today’s sitting of Letterkenny District Court.
He was also charged with two other robberies, both at the Glencar Express Shop in Glencar, Letterkenny on January 9th and 24th last.
It was a shop which Mitchell visited three to four times a day.
The court heard that during one of the robberies, Mitchell grabbed a bundle of notes amounting to €835 which was later paid to a drug dealer.
Solicitor for the accused Frank Dorrian said Mitchell had been on drugs since he was 12 years old and had used a wide range of drugs and had now become addicted to heroin.
He said he was not normally violent but the attack on the shop assistant was borne out of desperation.
Judge Paul Kelly said he appreciated Mitchell addiction problems but said the public had to be protected.
“This a horrific catalogue in this man’s relatively young life. I can’t have a lot of sympathy for him.
“In this case a young lady was going about her job and suffered a nasty injury in her attempts to do just that. Whatever the motivation may have been for this, the public has to be protected,” he said.
Judge Kelly sentenced Mitchell to a total 12 months in jail on the various offences.
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