He is entitled to credit (meaning the court can't decide not to award credit) for days spent in jail on any sentence where the underlying matter was the cause of his incarceration before disposition. You've asked several questions here and in your post about ten minutes before. The combined background facts are not entirely clear. If he posted bond before his PO requested that he be detained, then the only sentence to which he would be "entitled" to credit time would be against the violation sentence to be imposed. If there were days left not needed as credit against that sentence the Court could, but is not required to apply that against the sentence on the new charge. In my experience if that situation obtained the court would likely grant credit anyway. If he has not posted bond on the new charge then either or both sentences (if there is a sentence imposed on the new case) would be entitled to credit but not both unless the court directed the violation sentence to be served concurrently. Without a conviction on the new charge he's likely in violation of his probation on at least to technical violations, the new arrest and consumption of alcohol and/or controlled substance. Being that he is on probation he situation and the due process to be accorded is different then an individual who is not on probation when arrested on new charges. There is no reason to anticipate that it will take 9 months to dispose of either of his problems unless he were to be responsible for substantial delays. If he does not yet have counsel, I would expect him to have representation soon. If private counsel is retained it will be very soon. Counsel can petition the court to lift the detainer if there are good grounds to support that request. A good and experienced attorney would be of great benefit in such an effort; he can, however, be detained until the new charge is completed. If convicted he will face a violation hearing as a convicted violator. He needs good counsel badly now.
The defendant's attorney can attempt to negotiate a plea that calls for the time to run at the same time as the time being served on the first case. The credit is not automatic and must be negotiated or up to the Judge to run it at the same time.
Your question is not really clear. You can only receive credit for time spent in jail on that charge. Most places will give credit for two charges at the same time.
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