Flack is accused of shooting to death Andrew Stout, Steven White, Kaylie Bailey and Bailey's 18-month-old daughter, Lana-Leigh in May.
The bodies of the older three victims were found at Stout's Ottawa, Kan., farm. Lana-Leigh's body was found several days later in a suitcase in a creek.
Franklin County Judge Thomas Sachse on Wednesday said Flack will stand trial on charges of capital murder, first-degree murder and criminal possession of a firearm, WIBW-TV, Kansas, reported.
There was no word whether prosecutors would seek the death penalty.