It can be a useful source of bargaining power to use experts on your side in a negotiation. Clearly they are there for their expertise, not to make decisions for you but I would query whether it is always best to take them out of the negotiation at critical points.

Some people, such as Mark Suster in this article ( express the view that using 3rd parties to negotiate on your behalf should be restricted to a minimum so that you can keep control of your deals. It is true that often we as the decision-maker will have more at stake than the expert does. It is also true that for that same reason we might handle the negotiation differently than they would. However, their detachment can actually be an advantage. Often when our personal interests are at stake we invest the deal-making process with too much emotion. This can cause us to get anxious or aggressive or inhibit us from making decisions. As a result we might end up over playing or under playing our hand.

When we use experts their lack of emotional involvement can be an advantage. It can cause them to view matters more calmly and dispassionately in the heat of the negotiation, enabling us to make better decisions when they refer matters to us for instruction.