Jasim Uddin went in front of Nusrat's house last night by an auto-rickshaw and acted suspiciously there.
Police detained a man in front of the house of Nusrat Jahan Rafi for suspicious behaviour early today.
The arrestee is Jasim Uddin.
Confirming the matter, Police Superintendent of Feni Khondakar Narunnabi said, "Jasim Uddin went in front of Nusrat's house last night by an auto-rickshaw and acted suspiciously there."
"Jasim's brother said that Jasim is not mentally stable. Jasim will be handed over to his brother soon." Narunnabi added.
Nusrat's elder brother and the local union council interrogated the auto-rickshaw driver.
It has been alleged that miscreants are threatening Nusrat's family since the verdict was announced. Police guard has also been strengthened at Nusrat's house.
Nusrat Jahan Rafi, a student of Feni's Sonagazi Islamia Senior Fazil Madrasa, was set on fire on April 6 this year for refusing to withdraw a case against her madrasa principal, Siraj Ud Doula, for sexually assaulting her in March. She died on April 10 at Dhaka Medical Hospital.
A Feni court on October 24 sentenced all 16 accused to death in Nusrat murder case.