According to police sources Subhash was arrested after the investigators came across circumstantial evidences into the incident.
The Crime Branch team, which probed the case, suspected that Subhash pushed the victim out of the train after she spurned his proposal to marry him.
The research student of NIT-Kozhikode, hailing from Thiruvananthapuram, died by falling into the Periyar river when the train was passing through the Aluva Bridge near Kochi on April 24, 2011.
It was Subhash, travelling with her, who informed the railway police of the disappearance of the researcher. Her body was found from the river a few days back.
The railway police initially dismissed the incident as a case of suicide. However, Kerala High Court ordered an investigation by the Crime Branch based on a plea from her father.