Tugela, you apparently are not aware (or not recognizing) that this is not really a local trial, even though there are local players involved in the parts of the process. Legally it is a State of Tennessee matter.
* The crime is one against the law of the State of Tennessee,
* the charges are issued from the State of Tennessee,
* the prosecutor is for a district of the State of Tennessee,
* the trial is held in a court of the State of Tennessee, and
* any verdict and punishment will be administered by the State of Tennessee.
Responsibility for obtaining and supplying discovery rests with the prosecutors, not the investigators. If the investigators don't cooperate then presumably the prosecutors could get a court order to force them to, but supplying discovery is not an obligation for the investigators.
That is simply not accurate, in the ultimate sense of things. The responsibility to supply discovery ultimately rests on the State of Tennessee, not being limited to any one person or office working for the state apparatus.
The prosecutors have an obligation to exercise due diligence to ensure that all discoverable materials are available.
This obligation is on Tennessee as a whole, and the fact that the prosecutors would be the ones tasked with gathering the evidence and providing it to the defense does not mean that the prosecutors, in a legal sense, are the only ones with that constitutional responsibility.
Essentially any information made available to them can't be concealed, but if the investigators don't inform them of the existence of relevant information then they will not be in a position to turn it over as discovery.
You're making a distinction here as if this creates an exception in the law. It does not.
Here's the key point. If the individual prosecutory team in a criminal trial does not have all the exculpatory evidence gathered by the state, and therefore does not share all the exculpatory evidence with the defense, then the burden of providing discovery has NOT been met by the state, and the trial process has been done in a way that violates the rights of the defendant(s).
Also, the jurisdictional investigative agency is the local sheriffs department, not the TBI.
Not really true. But again, who did the investigating and gathered the evidence for the "state" really doesn't matter, when it comes to the trial. Constitutionally, the ones doing the prosecution MUST turn over
all exculpatory evidence that has been obtained by the state, and that legal obligation ends only when all of that has been provided. It does NOT end or vanish if the prosecution team fails to fully obtain it from all investigatory agency(s), and penalties would be applicable.