Four Supreme Court justices skipped the State of the Union address: Antonin Scalia, Sonia Sotomayor, Clarence Thomas and Samuel Alito. Alito, at least, had an excuse: he was signing an order to stay the execution of a Missouri death row inmate.
Herbert Smulls was scheduled to be put to death at 12:01 a.m. Wednesday by lethal injection. The drug that would be administered to Smulls would come from a compounding pharmacy, since makers of the drugs that used to be used for lethal injections have since banned their use in capital punishment. Missouri is one of several states that has had to scramble to replace those drugs with new, untested alternatives.
Missouri refused to disclose which pharmacy supplied the drug it would use to kill Smulls, which his lawyer argued would make it impossible to know if he would face pain and suffering when it was administered. For one, the drug that will be used to kill Smulls has been stored at room temperature for several days longer than pharmacy industry standards dictate. Though Missouri's governor Jay Nixon and federal courts denied Smulls' appeal for clemency, Alito signed a temporary stay just two and a half hours before Smulls was scheduled to be killed.
Smulls was given the death penalty for killing the owner of a jewelry store during a robbery in 1991.
Had Alito not been busy staying Smulls' execution during the State of the Union address, it's unlikely he would have attended. In 2010, Alito visibly mouthed the words "that's not true" when President Obama criticized a recent Supreme Court decision and later remarked that justices "have to sit there like a proverbial potted plant most of the time." He hasn't been to a State of the Union address since.
Update, January 29: Smulls has been executed by lethal injection.