Neha Shrama, a nanotechnology researcher, was found dead under mysterious circumstances in her laboratory on March 16 at a private educational institute here.
The sketches drawn by the Crime Branch of the Delhi police, show a long-faced man in his twenties, lean and with short-cropped hair; a second young man with a round face, also in his twenties; and a third aged between 30 and 35 with curly hair.
The sketches, released last evening by the local police, were drawn after questioning a number of students and employees of the university, police sources said.
Meanwhile, a group of protesters reached the office of the SSP last night and alleged the use of third-degree methods during the police interrogation of Dilip, a guard at the university, to make him tell about suspects for the sketches.