ST. LOUIS (AP) — A Missouri federal judge is refusing to block next week’s execution of a cancer-stricken inmate who used a hammer in killing three workers of convenience store more than two decades ago.

U.S. District Court Chief Judge Greg Kays in Kansas City, Missouri on Tuesday threw out Ernest Lee Johnson’s request to intervene.

Johnson claimed in an appeal filed last week that his brain tumor constitutes a “unique medical condition” that could be exacerbated by Tuesday’s scheduled lethal injection, possibly causing uncontrollable seizures and convulsions.

The state counters Missouri has carried out 18 rapid, painless executions since late 2013. Kays also sided with the state’s argument that 55-year-old Johnson’s appeal wasn’t filed timely enough.

Johnson was convicted of killing three people in 1994 at a Columbia convenience store where they worked.