A forensic accountant can contribute significantly to a securities fraud case. These professionals specialize in tracking down odd payments and unauthorized charges. While they may be expensive, in they end they may be worth every penny you pay them.
Keep in mind that when you sue for securities fraud, you're suing the brokerage or investment company, not a particular broker, even if they're the one who broke the law. Don't let a sob story on anyone's part slow you down; it's up to the company to keep a tight rein on its brokers.