Standard of Proof Required:

Probation

Probation:  A probation search with no warrant, probable cause, or even reasonable suspicion, so long as it does not exceed the scope of the consent given, and is not done for purposes of harassment or some arbitrary or capricious reason, meets, in the opinion of the California Supreme Court, both federal (Fourth Amendment) and state (Art. 1, § 13) constitutional requirements.  (People v. Bravo (1987) 43 Cal.3^rd 600; People v. Brown (1987) 191 Cal.App.3^rd 761; see also People v. Reyes (1998) 19 Cal.4^th 743.)

This includes juvenile probation.  (In re Tyrell J. (1994) 8 Cal.4^th 68, overruled on other grounds.)

The Ninth Circuit Court of Appeal has, as a rule, assumed that, at the very least, a "reasonable suspicion" of renewed criminal activity is required for both parole and probation Fourth Waivers.  (See United States v. Stokes (9^th Cir. 2002) 292 F.3^rd 964; "reasonable suspicion" found, so the issue not discussed.)

However, most recently, the Ninth Circuit has conceded that this issue is really not yet settled, at least sufficiently to hold an officer civilly liable.  (Motley v. Parks (9^th Cir. 2005) 432 F.3^rd 1072, 1083-1088; officers entitled to qualified immunity on this issue. See below.)

The Supreme Court has specifically left open the question whether or not a probationer on a Fourth Waiver may be searched on less than a reasonable suspicion.  (United States v. Knights (2001) 534 U.S. 112, 120, fn. 6. [[151 L.Ed.2^nd 497].) 

Until the U.S. Supreme Court does rule on this issue, it is acknowledged that the California rule is that no suspicion is needed to conduct a Fourth wavier search on a probationer.  (People v. Medina (2007) 158 Cal.App.4^th 1571; probationers having "consented" to warrantless, suspicionless searches.)

But in Samson v. California (2006) 547 U.S. 843 [165 L.Ed.2^nd 260], the Supreme Court hinted strongly that although a suspicionless search of a parolee is constitutional, probationers probably have more rights than parolees and may require a higher (i.e., a "reasonable suspicion") standard.  

Parole

Parole:  Older California case authority to the effect that a police officer needs a "reasonable suspicion" of renewed criminal activity before conducting a parole Fourth Waiver search (See People v. Burgener (1986) 41 Cal.3^rd 505, 534-535.) was overruled in People v. Reyes, supra.

In Reyes, the California Supreme Court adopted the reasoning of In re Tyrell J. (1994) 8 Cal.4^th 68, overruled on other grounds, and, overruling Burgener, determined that as with juvenile probationers, parolees do not retain a reasonable expectation of privacy, and may therefore be searched even without even a "reasonable suspicion" of renewed criminal activity or other parole violation. 

The Ninth Circuit Court of Appeal avoided deciding the issue in a number of recent cases.  (See United States v. Crawford (2004) 372 F.3^rd 1048; Moreno v. Baca (9^th Cir. 2005) 431 F.3^rd 633; and Motley v. Parks (9^th Cir. 2005) 432 F.3^rd 1072, 1083-1088.)

The United States Supreme Court has now unequivocally settled the rule, agreeing with California's analysis of this issue, at least as it relates to parolees.  (Samson v. California (2006) 547 U.S. 843 [126 S.Ct. 2193; 165 L.Ed.2^nd 260]; search of a parolee's person.)

See also United States v. Lopez (9^th Cir. 2007) 474 F.3^rd 1208, 1212-1214.) where the Ninth Circuit Court of Appeal followed Samson in finding that a suspicionless parole Fourth Waiver search of a parolee's residence was valid.