"Police inaction in cases involving violence against Dalit women is unfortunately disturbingly common. Even in this case, the police failed to act on earlier complaints from the family," said Rekha Raj, programme manager, women's rights, at Amnesty International, India.
"The failure of the police to investigate previous complaints about caste-based discrimination and harassment against the woman's family must also be investigated," Ms Raj said.
"Dalit women face multiple levels of discrimination - from the community and often from the police. The Kerala government must hold the police accountable for any inaction on their part," she added.
According to local police, the woman, a law student, hailing from a poor family was raped and brutally assaulted using sharp edged weapons before being murdered at her house at Perumbavoor in Ernakulam district on April 28.
Three men have been detained in relation to the killing. "We have complained earlier against certain individuals who used to threaten us, but the police did not take any action," the law student's sister told Amnesty.