How about a civil suit against the prosecutor for wrongful prosecution ?
Prosecutors are generally immune from such suits unlessthey were involved in the investigation and were negligent in conducting/supervising it. if earle was involved in the actual investigation, he might be open to a civil action. The big problem there is that a grand jury indicted deLay, so Earle would have a pretty good defense.
There is a state tort called malicious prosecution. There is also federal civil rights actions. The former is darn near impossible due to sovereign immunity issues. The latter likely requires evidence DeLay won't be able to get.
We've essentially got a government that has granted itself immunity from virtually any wrong doing.