While sharing a case can be in the best interest of the client be cautious about making sure you document the relationship. Any time a law firm shares a case with another attorney or refers a case out to another firm, the original law firm continues to have exposure for this case. Numerous courts have allowed plaintiff attorneys when pursuing attorney malpractice claims to include all attorneys and law firms that have touched a case.
It is important to document with the client the referral with a written agreement that spells out the referral or case sharing understanding. Even if the attorney is not taking a fee for the referral, it is good practice to document and have the client sign any referral to another attorney. If there is no fee involved you should have a client signed document that you are not representing your client in this matter and have any involvement. You should consult your local bar for the appropriate forms and wording for your jurisdiction.
If you are case sharing or referring cases to other attorneys at a very minimum make sure and require that the referring firm has attorney malpractice coverage with the limits and deductible that you are comfortable with given the matter being referred.
At a very minimum, a copy of the declarations page showing limits, deductible and prior acts dates should be obtained annually. Better practice is to get a certificate of insurance from the firm that the case is being shared with showing your law firm as a certificate holder. The advantage of being a certificate holder is that if the coverage is cancelled during the policy term, the certificate holder should be notified.