A warrant will be issued for your arrest and assuming the court warned you of the consequences of not showing up for your re-trial, the re-trial could proceed in your absence. Not returning to court is a very bad idea.
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A bench warrant would be issued on the case and the person could also be charged with bail jumping, which gnerally requires consecutive time.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 385-8015 or via email at Eric@RothsteinLawNY.com. The above answer is for informational purposes only and not meant as legal advice.