Kanta Mukherjee said Mamata Banerjee had last appeared before the court as a prosecution witness in 1994.
Lalu Alam, accused of brutally attacking West Bengal Chief Minister Mamata Banerjee nearly three decades ago, was on Thursday acquitted by a city court for want of evidence.
Sixth additional district and sessions judge, Alipore Court, Pushpal Satpathy, passed the order on a plea by the prosecution that the case be considered for closing as time has elapsed in the trial, which is yet to reach any conclusive stage, and many witnesses have died over the years.
After hearing the defence lawyer and Alam, the court found that he may be acquitted for insufficient evidence, public prosecutor Radha Kanta Mukherjee said.
Judge Satpathy had on August 21 closed cross-examination of witnesses in the case on a prayer by the prosecution.
The Trinamool Congress chief was last month summoned by the judge to appear as a prosecution witness and evidence-in-chief, but she could not make it owing to exigencies and security issues, the public prosecutor said.
Defence lawyers could not make arrangements for video-conferencing, he said
On August 16, 1990, Mamata Banerjee, then a Youth Congress leader, was hit with a blunt weapon on the head apart from blows on her body that caused grievous injuries. She had to spend several days at a government hospital for treatment, according to the prosecution.
The attack on her by Lalu Alam, brother of then CPI(M) leader Badshah Alam and others, had catapulted Mamata Banerjee to limelight as a firebrand Congress leader.
Public Prosecutor Kanta Mukherjee had told judge Satpathy that as 30 years have passed since the incident and the trial is yet to reach any conclusive stage, the court may take a call on its continuance.
He had also prayed that the court may pass an order keeping in mind the principle of natural justice.
Lalu Alam, who is out on bail, is being tried in the case at present, while 11 other accused are either deceased or not traceable, Kanta Mukherjee said.
The public prosecutor also told the court that the process is likely to continue for many more years, and would only lead to harassment of all involved in the matter.
Kanta Mukherjee said that Mamata Banerjee had last appeared before the court as a prosecution witness in 1994, but the defence lawyers had refused to cross-examine her then, saying they would do so along with the other witnesses in the case.
Owing to security issues, it had been decided that she will appear before the court through video-conference, but the arrangements could not be made in the court, the public prosecutor submitted before the court.
He also said that several key witnesses in the case have died over the years, including former chairman of Kolkata Municipal Corporation Anil Mukherjee and three other former councillors -- Dibyendu Biswas, Dilip Majumdar and Anup Chatterjee.