Building Blocks

November 1, 1999

Richard Morgan is a founder member of SCL. He now acts as anindependent consultant and can be contacted on 0181 505 5847 or by e-mail at

Among the rights of data subjects in the Data Protection Act 1998, wefind (in s 14) Rectification, blocking, erasure and destruction. The 1984 Act (s24) had spoken only of Rectification and erasure. If we leave aside for themoment the difference (if any) between erasure and destruction, we must notethat blocking is new in this context.

Blocking is nowhere defined in the Act, but the Oxford Dictionary gives thefirst meaning of the word as ‘to put blocks in the way’ and hence ‘toobstruct’, and later ‘to shut up or in by obstructing ingress and egress, toprevent access to or exit from’. I take it that in the Act it means‘preventing disclosure’, though I have to say if it is a term of art in theIT world it is not one I have ever come across.

Databases are constructed on the assumption that data will be added, amendedor erased (destroyed if you will), so in appropriate circumstances there shouldbe no difficulty for a data controller in complying with rectification, erasureor destruction. But blocking is different. If the disclosure which wouldotherwise take place but for the blocking is under the direct human control ofthe data controller, again it should not be difficult to inhibit it. But if itis some automatic process which prints out and sends data to a class ofrecipients at regular intervals or on the occurrence of certain events, it maybe quite difficult to add an extra field or otherwise prevent one record fromfollowing this procedure. It is notoriously difficult to add extra fields torecords and a blocking maker might well be such an extra field.

Section 14(2)(a) also raises the possibility of ‘requiring the data to besupplemented by such statement of the true facts… as the court may approve’.This wording exactly copies that in s 24(2)(a) in the 1984 Act and again raisesthe need for an extra field in the file. I do not know anyone who has everprovided such a field but with the addition of blocking to the list of rights ofdata subjects, data bases of personal data should certainly from now beconstructed with extra field(s) both for the statement and blocking.