Habeas corpus petitions are the remedy of last resort for inmates who want to get out of jail. To win, you have to show that your state court conviction violated the U.S. Constitution. Since you have to show that the conviction violated federal law, the defendant here does not get a new trial.
The case is Freeman v. Kadien, decided on July 3. Freeman was convicted of, among other things, vehicular assault and DWI after he cut someone off on the Thruway, causing an accident and seriously injuring another motorist One piece of evidence against him at trial was obtained from a blood draw pursuant to a warrant that violated state law. (Freeman refused a breathalyzer test and the prosecutor got a warrant to draw Freeman's blood). The state Appellate Division said this evidence was harmless error. Since that is a state law determination, it cannot support a habeas claim.
There is no violation of federal law. That kills the habeas petition. Normally, to challenge a state court conviction, you have to show that the state court error had a "substantial and injurious effect" on the case. That only applies to errors of federal law. While the Appellate Division said that the erroneous evidentiary ruling was harmless, that's a state law determination, not a federal one. The Second Circuit (Raggi, Sack and Koeltl [D.J.]), says, "a harmlessness determination regarding an underlying error of state law does not implicate a freestanding constitutional right. Rather, the harmfulness of evidence admitted in violation of state law is itself a question of state law to which the federal 'substantial and injurious effect' standard does not apply."