Never do it; it will only hurt your case. Insurance adjusters are trained to ask certain, specific questions which are intended to make the strongest personal injury claims look weak. Here is a great post regarding recorded statements, and their pitfalls from Maryland personal injury attorney Ronald Miller over at his Maryland Injury Lawyer Blog:
Most insurance adjusters tell personal injury lawyers that they need a recorded statement from the lawyer's client to "firm up liability" or to "assess credibility." But providing a recorded statement is typically a "loose-tie." It rarely results in a finding on liability in favor of the accident attorney's client. Of course, this is not to say that this is always the case, but absent special circumstances, the downside far outweighs any benefits.
Defense attorneys use recorded statements to parse sound bites out of context, often giving ample fodder for cross-examination against your personal injury client at trial.
A critical caveat is in personal injury accident cases involving an uninsured or underinsured case. Because these claims are breach of contract cases, the accident lawyer's client's insurance policy almost certainly contains language making a statement to the uninsured motorist carrier a condition precedent to the accident victim's recovery under the policy.
The personal injury attorney should not assume compliance is necessarily required. This is particularly so in cases where the claim was denied. The accident lawyer should check to see when the claim was denied. If the claim was denied before the claim representative requested the recorded statement, the lawyer may have grounds for refusing a statement, claiming breach of contract. If this is the case, the lawyer should set up this claim in writing with the claims adjuster
If your client must give a statement in an uninsured motorist case, the best way to avoid disaster is to treat it as if the lawyer were prepping the client for his or her deposition. The accident attorney should discuss the client's statement with the client before he or she gives it and should generally have the client give the statement at his or her office. The lawyer should participate in the call the client makes to give a recorded statement, and should object to improper questions, remembering the Maryland Rules or the attorneys' local rules of procedure do not apply, giving the lawyer far more latitude. Finally, let the claim representative know you insist on a copy of the statement.