In Illumina v TDL & Ariosa  EWHC 1159, an interesting question at hand was whether Illumina had to get the Court's permission to rely on expert evidence which was used in a different case and then served under a hearsay notice in the present proceedings.
This is of particular interest because CPR 35.4 provides that "[…] no party may call an expert or put in an expert's report without the court's permission."
The present 2019 proceedings, heard by Mr Justice Carr, concerned the second of two related cases, the first of which was heard in 2017. In the 2017 proceedings, an expert report of Dr Erlich was admissibly filed. In the present proceedings, Illumina filed that same expert report as a hearsay notice.
Ariosa argued that Illumina could not simply introduce Dr Erlich's report into proceedings in this way, since the Court's permission would first be required.
Mr Justice Carr explained that, in civil proceedings, evidence shall not be excluded on the ground that it is hearsay, though a judge should exercise discretion in attaching appropriate weight to that evidence.
He then went on to say that it is important to have regard for the definition of 'expert' as contained in CPR 35.2: "a reference to an 'expert' […] is a reference to a person who has been instructed to give or prepare expert evidence for the purpose of proceedings."
In Rogers v Hoyle  EWCA Civ 257, the term 'proceedings' in CPR 35.2 was interpreted as meaning the current proceedings.
As such, Mr Justice Carr decided that no permission of the Court was needed, and the expert report was prima facie admissible as evidence.
In order to address concerns of whether his finding would lead to numerous hearsay notices being filed to introduce old reports into new cases, Mr Justice Carr noted that the Court still retains control of evidence to be adduced by way of its discretionary powers to exclude evidence under CPR 32.1.
Consideration should be given to the possibility of the introduction of previous expert reports into proceedings that closely resemble the previous case(s) in which those expert reports were first admissibly served.