A YOUNG robber's mother became hysterical as her son was sent to prison for six years, screaming he had committed the crime out of love. 'He was just trying to help me out with my medical bills,' Leung Yee wailed yesterday. 'It's not fair! It's the first time my son has done something wrong!' Ms Leung said the sentence was far too severe. She vowed to appeal. Yeung Chi-sui, 20, was paid $700 for his part in an armed robbery at an illegal dental clinic, the court heard. The gang gave their victims bus money after they complained that the raid would leave them stranded. Defence lawyer Michael Vidler, representing Yeung, told Deputy Judge Duggan his client had committed the crime to help fund his mother's breast cancer treatment. Yeung's co-conspirators, Chan Kam-po, 16, and Kwok Chak-ming, 20, were also found guilty of robbery and sentenced to six and seven years respectively. Choi Ming-lun, 16, admitted the charge and testified against the others. He was given four years. Chan and Kwok were also convicted on a second robbery charge. Crown prosecutor Hui Ka-ho said the sentences imposed were on the high side but were not excessive. The gang burst into the unlicensed clinic on June 3 last year after one pretended to have a toothache. Dentist Tsang Chum-wo was having dinner with his wife and daughters at home in Tuen Mun. When the bell rang, he found four young men on his doorstep. One claimed to be suffering from toothache. Mr Tsang let him in and led him into a storeroom. But the other three forced their way into the house. One went into the storeroom and pulled out a 10-centimetre knife. A second produced a similar weapon. When Mr Tsang struggled, the blade was pointed at his wife's waist. His daughters were locked in another room. The men then gagged Mr Tsang and bound his wife's hands with tape. They stole jewellery and $1,500 cash. When the victims complained the robbers were leaving them without bus money, they returned $100. The District Court heard Chan and Kwok had robbed a woman of $200 and valuables inside a lift on a separate occasion.