You are a lateral hire.

You are an expert in a specialised field.

So, what happens when you find yourself on the other side, acting against your old firm's clients?Until a few years ago it was unusual for partners in commercial law firms to move on, but the practice is now widespread and has serious client confidentiality implications for both solicitors and clients.This type of prob lem has recently been considered by Mr Justice Lightman in a High Court action seeking an injunction against a Hammond Suddards partner (Re A Firm of Solicitors, 5 May 1995).The substantive action (the patent case) is between two large international companies involved in diagnostic medicine and concerns alleged patent infringement.

The litigation is one of the most extensive and complex pieces of intellectual property litigation presently before the English courts.In March 1995, the defendant to the patent case decided to appoint a new firm of UK solicitors and appointed Hammond Suddards.

The Hammond Suddards team was led by Laurence (Larry) Cohen, referred to by Mr Justice Lightman as one of the UK's foremost intellectual property litigators.

Mr Cohen's personal control of the litigation was an important factor in the defendant's choice of Hammond Suddards.Prior to joining Hammond Suddards in October 1992, Mr Cohen had been a partner in one of the foremost firms specialising in the field of intellectual property, a firm which has at all times acted for the patent case plaintiff.The first action in the patent case started in February 1992 at a time when Mr Cohen was still a partner at that firm, but Mr Cohen (who was engaged entirely on other work for different clients) was not in any way involved in the proceedings.Nonetheless, the plaintiff sought an injunction to prevent Mr Cohen (but not Hammond Suddards) being involved in any part of the patent case on the grounds that he might be in possession of confidential information by virtue of being a partner in his old firm in 1991/92.The plaintiff was unable to say what, if any, confidential information Mr Cohen might have received, or in what circumstances, and accepted Mr Cohen's statement that he could not recollect receiving any confidential information.This can be compared to another recent case Pavel v Sony (12 April 1995) in which it was alleged that Hugh Laddie QC was aware of confidential information relating to Sony's case as a result of tea room banter with Robin (now Mr Justice) Jacob.

Bingham MR accepted that Mr Laddie could recollect no such discussion, that Mr Jacob would not have breached client confidence in this way and that, Mr Laddie's integrity being beyond doubt, there was no case for Mr Laddie to answer.Unsurprisingly, and happily for solicitors, Mr Justice Lightman made a similar finding, holding that Mr Cohen did not have any relevant confidential information and so was free to act for the defendant.In giving judgment, Mr Justice Lightman set out the test relating to solicitors who move firms.

Where a firm of solicitors is retained, a solicitor will only be disqualified from acting in a contentious matter against his previous firm's clients if he or she has (or there is a real risk that he or she has) relevant confidential information; that is, information which was confidential at the time of communication and which remains both confidential and relevant.Mr Justice Lightman said that the solicitor must prove that he or she has no relevant confidential information.

Mr Justice Lightman was at pains to observe that Mr Cohen's 'honesty, integrity and good faith is in no wise challenged' and held that the facts failed to indicate that Mr Cohen possessed any relevant confidential information.In focusing on the protection of relevant confidential client information as the basis of the court's intervention rather than matters of perception or previous relationships, the decision offers a workable rule.

In large law practices, handling many thousan ds of matters at any one time, partners and lawyers not involved in a particular case are rarely aware of confidential details of matters being handled by others unless specifically brought in for consultation.

If solicitors joining new firms were automatically, and without regard to the facts, prevented from acting against clients of their old firms, the concept of conflict of interest would be widened to a point of commercial impracticality.

Solicitors would find it difficult to move firms during their careers and litigation might be held hostage by tenuous conflict claims.As a result of the judgment there is some difference in the position of barristers and solicitors, the latter group alone bearing the (tricky) burden of proof to show that they hold no relevant confidential information.

Moreover, since solicitors work in partnerships and in direct relationship to the client, they may need to consider as a matter of practice management how best they can satisfy client demands for confidentiality.To achieve this, however, there is ample scope within the partnership agreement, within agreements with the client (including special retainer arrangements) and by adherence to internal procedures for protecting clients' confidential information.