A more thorough explanation:

The McNabb-Mallory Rule is a legal principle that requires police officers to promptly present defendants before a judge or judicial officer after arrest and excludes any confessions or evidence produced by police officers during the time period between arrest and the defendant’s initial appearance hearing.

The purpose of the McNabb-Mallory rule is to protect defendants from being coerced into self-incrimination. By requiring authorities to bring a defendant before the magistrate without unnecessary delay, the rule promotes defendants’ and courts’ interests in due process, efficiency, and equity.

The McNabb-Mallory rule has been codified into Rule 5(a) of the Federal Rules of Criminal Procedure. Most state penal codes have adopted Rule 5(a)’s mandate that defendants be brought before a magistrate judge without “unnecessary delay” (usually within 48-72 hours of arrest) – with delay measured as the entire duration of custody. If a defendant is brought into court late or is found to have produced confessions while in custody, they may have their suits dismissed on the basis of due process infringement.

For example, if a person is arrested for a crime, the police must bring them before a judge or magistrate within a reasonable amount of time. If they do not, any evidence or confession obtained during that time may be excluded from the trial. This protects the defendant's rights and ensures a fair trial.