All criminal cases in Tennessee and Georgia are not equal when it comes to material evidence being used to support the charges. There are indeed cases where the state has a solid claim for the filing, but there are also other cases that are filed on weak or even nonexistent evidence. Cases often take a long time to completely adjudicate, and evidence can fade if not disappear. Witnesses can forget certain material details, and evidence can even be lost within the chain of custody when communication problems exist. This is especially true with drug cases. And in addition, even the equipment used in obtaining evidence can be questioned regarding admissibility.
All evidence in a criminal case is available for inspection by criminal defense attorneys, and this is usually how case weaknesses are pointed out. Using DUI charges as an example, cases are sometimes prosecuted on officer testimony only when a suspect refuses a Breathalyzer or blood testing. In addition, even details such as the calibration record of a Breathalyzer device can be contested in establishing reasonable doubt when there is seemingly admissible documented evidence. And of course, there are also some cases where evidence has completely disappeared from official custody.
Prosecutors want to avoid a trial at all costs in most situations, but the trial is where the evidence will actually be tested. In lieu of a trial, prosecutors will generally be open to some level of charge reduction when it looks like their primary evidence has been compromised, also known as spoilation. Evidence that has been obtained in violation of constitutional protections can also be an advantage in building a criminal defense strategy, as the jury is not allowed to consider inadmissible evidence.
Spoilation is a common tool when criminal defense attorneys build cases for their clients, and especially when the client is being charged as an accomplice with a primary defendant. Intent must be established as well as the criminal act, and often tainted evidence can result in dismissal of all charges when effectively argued.