There is little doubt that the propriety of the  48 hour hold divides a lot of judges and lawyers. Professor Steven Mulory piece may not change your mind but it is worth reading.

Steven J. Mulroy (University of Memphis – Cecil C. Humphreys School of Law) has posted Hold On: The Remarkably Resilient, Constitutionally Dubious ’48-Hour Hold’ on SSRN. Here is the abstract:

For decades, various local jurisdictions used (and in some areas, still use) a constitutionally suspect procedure called a “48-hour hold.” A suspect is detained for up to 48 hours without charge while an investigation continues; after 48 hours, the suspect is either charged or released. The practice continues despite occasional criticism by courts, the bar, and the press. In many cases, this practice unconstitutionally detains persons without probable cause. Even where probable cause exists, the practice improperly circumvents rights to get bail, to get a prompt bail determination, and to be free of interrogation without the presence of counsel. While similar procedures may occur in other countries, it is contrary to American principles of criminal justice. Understanding why may also help in current debates over the proposed use of “investigative holds” of terrorism suspects.