The letter suggested that the girl, who is based in Delhi, should also be called as her testimony could prove vital to the case.
Taking cognizance of the six-page letter, presiding officer of the fast track court Purinder Vaidya Thursday asked prosecution and defence to assist the court in the matter.
Aman, 19, a first-year student of the Rajendra Prasad Medical College in Tanda town near here, died March 8, 2009, a few hours after being allegedly ragged by four final-year students.
A copy of the letter has been provided to both prosecution and defence, asking them to file their responses to it by Oct 8.
The letter also contained some mobile phone details. The anonymous writer claimed to be working with police.
Special Public Prosecutor Jiwan Lal Sharma said: "We have received a copy of the letter and the reply would be filed soon."
The court has fixed Oct 8 as the next date of hearing.
Aman's father Rajendra Kachru has deposed before the fast track court and narrated in detail the sequence of events that led to his son's death.
Kachru told the court Aug 28 that his son spoke to him in detail about the incident of ragging.
The court Aug 2 resumed the trial against four medical students -- Ajay Verma, Naveen Verma, Abhinav Verma and Mukul Sharma -- after they surrendered on cancellation of their bail by the Himachal Pradesh High Court.
The high court, which had initiated suo motu proceedings after bail was granted to them July 17, said: "The order passed by the trial court granting bail to the accused is against law... accordingly quashed and set aside."
"The trial court would ensure that the trial is conducted from day to day. The court would ensure that no undue and unnecessary adjournments are granted to either side," Justice D.D. Sud observed in a 37-page order.