Is a newly formulated constitutional rule to be applied retroactively or prospectively?

The decision whether a newly formulated constitutional rule is to be applied retroactively or prospectively depends on the nature of the right sought to be enforced and the purpose to be served by the new rule. Other factors to be considered are '* * * the extent of the reliance by law enforcement authorities on the old standards and * * * the effect on the administration of justice of a retroactive application of the new standards.' (Desist v. United States, 394 U.S. 244, 89 S.Ct. 1030, 22 L.Ed.2d 248, 255, quoting from Stovall v. Denno, 388 U.S. 293, 297, 87 S.Ct. 1967, 18 L.Ed.2d 1199.)