5.29.
As I noted at 1.48 above, Liberty had the disadvantage of having only the very
limited information made public in the open Operational Case. Eric King, who
also commented on the document, made the point that there was insufficient
information in that document for meaningful criticism or analysis of A8/5 to be
possible.
5.30.
I was able to consider each case study in considerably more detail, and with the
help of Cathryn McGahey QC and Gordon Meldrum, carefully examined possible
alternatives in these and all other case studies.
5.31.
Contact chaining, using data already acquired in respect of targets likely to be
linked to a subject of interest, is undoubtedly a valuable technique. But equally
plainly, it has limitations. In particular:
(a) Contact chaining depends upon:
•
the SIAs already knowing their initial subject of interest,
•
new subjects of interest being in contact with the initial subject,
and
•
it being possible to serve a targeted interception warrant on the
new subjects.
These conditions will not always be satisfied (particularly, in the case of
the third, in the overseas context): bulk interception offers other routes by
which new contacts can be discovered.
(b) The purpose of contact chaining is to find additional contacts who use the
same form of communication. But bulk interception may allow GCHQ to
find additional forms of communication between subjects of interest.
5.32.
In A8/5, the extremists were using a variety of different communications methods
in an effort to conceal their activities (a detail not set out in the open Operational
Case). Contact chaining would not have led to the identification of the unknown
email address. I am satisfied that, without bulk interception, it is very unlikely
that this email address and its user would have been identified.
5.33.
In respect of A8/10, bulk interception was used to identify an individual who was
taking great care to conceal his identity online, while engaging in child sexual
exploitation. GCHQ accepted that some of the results obtained through the use
of bulk interception could have been achieved through requesting targeted data
from CSPs in the UK and abroad. But GCHQ told me, and I accept, that these
sources tend to provide less complete information and are less satisfactory as a
means of identifying individuals who take sophisticated measures to avoid
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