There would be lawyers with security clearances, and the defendant would usually have to rely on his lawyer. It's not perfect, but it balances the conflicting

There would be lawyers with security clearances, and the defendant would usually have to rely on his lawyer. It's not perfect, but it balances the conflicting needs better than any alternative I've ever seen. Note that this isn't 1-sided in favor of the government. Consider what happens today. People working at Area 51 tried to sue over being exposed to toxins, but were stopped by the state secrets privilege. That privilege would die if we had classified courts.