What is the current state of the law on the right to delay in the course of an investigation?

"The Fourth Amendment does not require police officers to delay in the course of an investigation if to do so would gravely endanger their lives or lives of others." Warden v. Hayden, 387 U.S. 294, 298-99, 87 S.Ct. 1642, 1645-46, 18 L.Ed.2d 782 (1967). Police must be allowed to protect themselves before a potential threat of danger develops into a tragedy.