Search on suspicion
The Search and Surveillance Act 2012, s 6 (not yet in force) will allow a search warrant to be issued on suspicion that a relevant offence has been committed, is being committed, or will be committed. This suspicion must be on reasonable grounds.
The reasonable grounds requirement looks like a safeguard. But the current law requires reasonable grounds for believing that a relevant offence has been committed or will be committed: s 198 of the Summary Proceedings Act 1957. The higher threshold of belief in s 198 is replaced by suspicion in s 6.
Certainly s 198 is not perfect. The new law improves it by referring to offences that are being committed. There is also a complexity in s 198 because it includes reasonable grounds for believing that a relevant offence is suspected of having been committed. But that has not been the subject of careful judicial analysis, and the case law has focused on the difference between belief and suspicion that an offence has been committed. In the leading case, R v Sanders  3 NZLR 450, (1994) 12 CRNZ 12 (CA) the universal requirement of s 198 was held to be belief on reasonable grounds both in relation to the offence and to the finding of the evidence.
Both s 6 and s 198 require reasonable grounds to believe that evidence of the relevant offending will be found at the place to be searched.
The Law Commission recommended that the threshold of reasonable grounds for belief should apply both to the offending and to the finding of evidence. In NZLC R97 (2007) "Search and Surveillance Powers" the Commission said (Recommendation 3.1):
The Search and Surveillance Bill was so extensive and contained so many controversial measures that submissions do not seem to have focused on what has become s 6. I didn't notice it myself. Either everyone thought it was alright, or everyone overlooked it. There is no mention of it in the minority views in the Justice and Electoral Committee's report on the Bill.
The courts certainly think the distinction between reasonable grounds to believe and reasonable grounds to suspect is significant. See Collins v R  NZSC 3 at . In Britten v R  NZCA 81 at , Priestley J for the Court cited R v Williams  NZCA 52,  3 NZLR 207 at :
at p 461)."
The distinction is important too where there are powers of search without warrant. For example s 18(2) of the Misuse of Drugs Act 1975 permits warrantless search where there are reasonable grounds for believing in both the occurrence of a relevant offence and the presence of evidence. However s 20 of the Search and Surveillance Act 2012 replaces that with a power to search without warrant where there are reasonable grounds to suspect the commission of a relevant offence. (I note in passing that it is strange, given the opportunity to improve the law, that s 20 retains the rather technical and unrealistic requirements of s 18(2) as to identity of drug, particularly in view of the difficulty that they had caused the prosecution in Hill v Attorney-General (1990) 6 CRNZ 219 (CA)). The significance of the high threshold for warrantless search was emphasised in Hill by Richardson J at p 222:
We now seem to be intent upon eroding this general principle of requiring a belief, and a reasonable belief at that. Does our legislature's eagerness to grant powers to the police really reflect New Zealanders' wishes? Recent high profile searches have arguably given fresh life to Sir Thaddeus's reflections. We should reconsider this issue.
[Update] After I posted the above comments a colleague drew my attention to a recently published New Zealand Law Society Seminar Paper on the Search and Surveillance Act. There, the authors review the changes made to the grounds for issuing search warrants, in particular under s 6, and they conclude that the provision is balanced:
It doesn't surprise me that this was written by two prosecutors. They wrongly suggest that the belief as to the existence of the evidence is a protection of human rights and they overlook the erosion of the same rights created by the "[not] overly high factual foundation" of suspicion. It is easy to see that the belief in the presence of the evidence at a specified location is readily established: for example, if a reliable witness saw items being taken into a stated address, the reasonable grounds to believe they were there would be made out. That would say nothing about the requirement of the items being evidence of an offence, which is, under s 6, easily met by other information that gives rise to a suspicion of criminal activity. It is this element that protects - or should protect - reasonable privacy expectations.
It is fair to expect confirmation of my assertion that reasonable grounds to believe that a specified offence has been committed are required by s 198. In Rural Timber Ltd v Hughes  3 NZLR 178 (CA) the Court included in its description of the effect of s 198 the following:
And the form prescribed for search warrants, Form 50 in Schedule 1 to the Summary Proceedings Act 1957 materially as to paragraph (b) states:
"To every constable ... I am satisfied ... that there is reasonable ground for believing that there is in [the specified place, specified things] ... which there is reasonable ground to believe will be evidence as to the commission of an offence of [specified] ... ."
This applies the standard of reasonable grounds to believe to both the presence of the evidence in the specified place and to the link between it and the commission of a relevant offence.
A search authorised on lesser grounds, such as suspicion that a relevant offence has been committed and that the thing searched for will be evidence of that offence, will be a limitation on the right to be free from unreasonable search: s 21 New Zealand Bill of Rights Act 1990 (BORA).
Yet, on 12 June 2009 the Crown Law Office advised the Attorney-General that the search powers in what was then the Search and Surveillance Bill (now enacted, including s 6) did not give rise to unreasonable search and seizure in terms of s 21 of BORA. That ignores the restriction of the meaning of unreasonable search that is required for the new law to be accommodated. Unreasonable search will no longer include searches based on grounds that only amount to suspicion. The advice did not specifically address the terms of what is now s 6.
The Law Commission advised the Justice and Electoral Committee, which reported to Parliament on the Search and Surveillance Bill, that what is now s 6 does not substantively change the grounds for issuing a search warrant. (See the Interim Report on the Search and Surveillance Bill 45-1, p 10.) But s 6 is inconsistent with the Law Commission's Recommendation 3.1 quoted above which in turn is consistent with s 198. Plainly the point was overlooked, as there was so much in the Bill requiring consideration.