If you did read the article, then you'd have known that there are 166 people on trial. There would have been thousands of witnesses, forensic and other kinds of evidence, expert witnesses etc. that the court has to consider. Remember that the guiding principle of Indian judiciary is that "let a thousand guilty walk free, but not one innocent should be punished". Each of those 166 accused people are entitled to this protection from the judiciary - which means that each of those are entitled to defence lawyers, cross examination of each of prosecution witnesses and present witnesses and evidence of his or her own. This will naturally increase the length of the trial.
