Police inquiry revealed that the youth, L Manikandan, 20, of Velampudur village murdered his sister Arthi on Sunday night as he thought the girl as an obstacle for his relationship with a dalit girl in a nearby village.
However, his mother objected to his relationship citing the girl's caste. She dissuaded him stating that no one in their community (Vanniyar) would marry his sister, Arthi, if he married a dalit.
He continued his relationship with the dalit girl. A month ago, Valli found him speaking to his lover over the phone and picked up a quarrel with him. After that, Valli, his grandmother, brother Devan, 14, and Arthi stopped talking to him.
On Sunday night, Manikandan came home in an inebriated condition. Since Sunday was their turn to use a common well to water the crops, he woke his mother and brother up around 10.30pm. He forced them to go to their land to water the crops.
"When they left, leaving Arthi at home, Manikandan tried to commit suicide. But he changed his mind and decided to murder his sister thinking that she was the obstacle to his relationship," said Ranipet inspector of police D Rajangam.
He decided to get rid of Arthi. He smothered her with a pillow and strangled her using a nylon rope. When she died, he went to their farm. "Valli shouted at Manikandan for leaving Arthi alone at home. She rushed back home and found the girl dead," Rajangam said.
Growing suspicious, the police picked him for inquiry. On interrogation, he admitted to have murdered his sister.