Our police agencies are extremely good at it, and I'd venture to say the United States probably leads the industrialized world in confession rates. It's prima facie, direct evidence of guilt. Confessions in America relieve the prosecutor of the burden of proof . The best available defense strategy is to file motion for a suppression hearing . It's the only way to get the court to address the issues associated with whether the confession was proper or not.
Most states require that suppression motions be made prior to trial.
At suppression hearings, the defense attorney bears the burden of proof that a search was illegal or a confession was coerced. The only exception involves allegations that Miranda warnings were not given, in which case the state retains the burden of proof. Suppression hearings are best characterized as swearing matches over what really went on at the police station. Judges are reluctant to grant motions for them because they are restricted to an umpire role. The defense attorney who files them may be perceived as engaging in frivolous pretrial delay, but they have nothing to lose.