He has not been "...held to answer for a capital, or otherwise infamous crime...", if he were, he'd be entitled to due process, even as an illegal alien.
But he was in the country illegally, the court had found him to be gang member and ordered him to be deported. Illegal aliens are not entitled to the same rights, including due process rights, as Citizens.
If an illegal alien committed a murder, and was tried for it, if found guilty, they would have to serve their sentence prior to being deported. If they were exonerated, they could still be deported.