As Justice Oliver Wendell Holmes wrote,

Great cases, like hard cases, make bad law. For great cases are called great, not by reason of their importance in shaping the law of the future, but because of some accident of immediate overwhelming interest which appeals to the feelings and distorts the judgment.

Northern Securities Co. v. United States, 193 U.S. 197, 400–401 (1904)(Holmes, J., dissenting).

That idea seems to be on David Feige’s mind when he writes in Slate about the upcoming trial of admitted 9/11 mastermind Khalid Sheikh Mohammed:

No jury on this continent is going to acquit their client, the government is certain to insist on the death penalty, and KSM will almost certainly try to put the government on trial. So what’s a team of hardworking criminal defense attorneys to do?

Everything they can, which, in this case, will mean a lot of futile maneuvering that will generate a tragic flood of bad law, rendering the defense team’s valiant service not merely unsuccessful but actually hostile to the interests of all their other clients. …

In an idealized view, our judicial system is insulated from the ribald passions of politics. In reality, those passions suffuse the criminal justice system, and no matter how compelling the case for suppressing evidence that would actually effect the trial might be, given the politics at play, there is no judge in the country who will seriously endanger the prosecution. Instead, with the defense motions duly denied, the case will proceed to trial, and then (as no jury in the country is going to acquit KSM) to conviction and a series of appeals. And that’s where the ultimate effect of a vigorous defense of KSM gets really grim.

At each stage of the appellate process, a higher court will countenance the cowardly decisions made by the trial judge, ennobling them with the unfortunate force of precedent.

That’s surely a possibility. The trial of the admitted mastermind of 9/11 is, due to "immediate overwhelming interest," most certainly "great" under Holmes’ definition.

On the other hand, whatever apparent principles, rules or interpretations of law laid down by the courts in the prosecution admitted mastermind of 9/11 will be forever indelibly stamped with an annotation that the case involved no less than the admitted mastermind of 9/11.

Moreover, the courts, aware of the "greatness" and/or difficulty of the case, often make an extra effort to minimize the precedental value of their opinion.

Consider Bush v. Gore, certainly the "greatest" — at least in terms of immediate impact — legal ruling in recent memory, which openly instructed future courts to ignore it entirely: 

Our consideration is limited to the present circumstances, for the problem of equal protection in election processes generally presents many complexities.

Bush v. Gore, 531 U.S. 98, 109 (2000). Indeed, Bush v. Gore has been treated by many as a singular case that served a pre-determined goal rather than an evolutionary step in the progression of election law. For a number of courts, the case is downright radioactive due precisely to its "greatness."

Our Constitution’s protections for the criminally accused were drafted by a generation among whom treason was commonplace, then sculpted over eleven score years of rebels, thieves, gangsters, murderers and even a protracted civil war followed by decades of reconciliation and the integration of oppressed minorities into equal society in the face of socially-approved violence. Those protections can handle a couple trials of admitted mass murderers.