Kenneth Roth makes the case against preventative detention:
The most common argument against criminal prosecutions is that they examine crimes that were already committed, whereas the threat of terrorism is said to be so dangerous that it requires preventing acts before they occur. But the crime of conspiracy is sufficient to address today’s terrorist threat because it is both backward and forward looking.
Under U.S. law, a conspiracy can occur whether or not an intended illegal act has been carried out. Much as with the French crime of association de malfaiteurs, all that must be proved is that two or more people agreed to pursue an illegal plan and took at least one step to advance it. This should cover most terrorist plans: the lone wolf terrorist is rare, and al Qaeda and its spinoffs have typically relied on numerous participants to agree on a plan and pursue it. The same intelligence that allows investigators to identify and prevent a terrorist plot should allow them to prosecute the participants for conspiracy. Similarly, the crime of providing material support to terrorists can occur even when a terrorist act is only in preparation and has not yet been committed.
Another objection to conventional prosecutions is that they make it harder for interrogators to obtain information from suspects. Under the Sixth Amendment to the U.S. Constitution, a suspect facing criminal charges is entitled to a lawyer, who will generally tell his or her client not to talk to interrogators. But in fact, many criminal suspects with lawyers end up cooperating with interrogators because doing so can shorten the prison time they face. Moreover, the constitutional limits on a prosecutor’s ability to question a suspect without counsel need not interfere with parallel but separate questioning aimed at investigating other suspects or preventing terrorism. Even if a suspect’s right to counsel has been violated, the Constitution only prohibits prosecutors from using the information derived from the flawed interrogation at trial; it does not forbid other investigators, such as those trying to prevent future terrorist acts, from questioning the suspect without a lawyer present, so long as these investigators do not relay his or her words (or leads based on what he or she said) to the prosecution team. This division of labor may not be ideal, but it is better than resorting to preventive detention and discarding many basic due process rights.
Preventive-detention advocates also oppose criminal prosecution because many terrorism suspects have been subjected to torture and other harsh interrogation methods, the fruits of which no ordinary judge would admit at trial. This, they argue, makes criminal prosecution impossible. But it would be a perversion of justice to invoke the illegality of coercing evidence in order to justify the further trampling of suspects’ rights through preventive detention. Moreover, coerced confessions are not the only route to criminal convictions. A review of the hearings held before the Combatant Status Review Tribunals at Guantánamo shows that the government often possesses plenty of evidence unrelated to abusive interrogation — from computers and cell phones seized, financial records, and witnesses who have cooperated voluntarily. The U.S. government has tacitly acknowledged this point by reinvestigating the major Guantánamo suspects using allegedly "clean teams" in an effort to free prosecutions from the taint of previously coerced statements and allow them to go forward.
The Dish 