Police can use forensic search spider software that searches for key words and then is used to identify potential targets (people) for accessing their BBM records.
all they have to do is turn up at the RIM data hosting offices and with a suitable warrant they can demand entry to the computer servers and upload their forensic search routines. this will produce a list of targets, which they will then verify with RIM and a legal team as being suitably relevant based on the search criteria they used.
once they have an approved list of targets signed off by the legal team, they can demand all the data from those targets and once they have it, they then scan the data for each target and highlight those they want to take formal copies of the records. so long as the legal team approve the fact there is enough evidence to warrant the use of the information, then this is copied and is admissible evidence.
if the legal team don’t accept the justification for use of any targets data, then it’s not admissible and thus not copied.
it’s not a quick process, but is very useful for gathering data for further investigation.