One of the misconceptions I frequently hear as a Denver criminal defense attorney is that a retainer is simply a fee that you pay to your lawyer at the beginning of the case that you'll never see again. While it's true that it's unlikely that you'll get much of your retainer back, this is not true for important reasons. In reality, the retainer is a security that you will pay for the legal services. It's like a deposit for your rent. The attorney is not allowed to use the money for anything until he earns the money. That means the money must be kept in a separate account until the attorney "earns" the money, or actually does legal work to the value of the money. Technically, the money in the trust account is still yours until the attorney bills for the work, on either an hourly or fixed fee basis (attorneys that represent clients in contingency fee cases generally do not take a retainer since they front the costs of the case until the judgment comes down). It's an extremely serious ethical violation to take money from the trust account before it is earned, or mingle it with personal funds.
An additional question many Denver criminal defense attorneys get is whether you have to pre-pay for everything. Generally, attorneys vastly prefer that you give a retainer for the cost of the entire case. That's because we're lawyers, not bill collectors! However, you may be able to negotiate some sort of payment plan. This will typically involve paying half the fee up front, then an equal second payment. To secure the second payment, the lawyer will usually ask for a credit card to authorize up front, or a post dated check. Additionally, you'll usually get a discount for prepayment. However, if it's not possible, be sure to ask your defense lawyer about the possibility of a payment plan.