RPF Constable Chetan Singh, who gunned down three passengers and a superior on the Jaipur-Mumbai Central Express last month, on Friday refused to undergo a narcoanalysis test after the Government Railway Police (GRP) sought the Borivli metropolitan magistrate court’s permission to carry out the procedure on him. 

According to sources, Singh was produced before the court on Friday and the GRP sought three days of additional police custody of the accused as well as permission to make him undergo brain-mapping, polygraph and narcoanalysis tests.