WICHITA, Kan. — Religious conservatives have dusted off a largely forgotten 1887 state law that allows citizens to launch grand jury investigations, and they are using it to help turn Kansas into one of the nation’s biggest abortion battlegrounds.

A grand jury that was impaneled January 8 by way of a citizen petition drive is investigating Dr. George Tiller, a Wichita clinic operator abhorred by anti-abortion activists because he is one of the nation’s few physicians who perform late-term abortions.

This is the second such citizen investigation of Dr. Tiller since 2006.

Phillip Jauregui, counsel for the anti-abortion Life Legal Defense Foundation, said Kansans are invoking the 19th-century law because prosecutors are too soft on abortion.

“This is a right the people of Kansas have given themselves,” he said.

But others say the law is a dangerous tool.

“This is a witch hunt — plain and simple,” Vicki Saporta, president of the National Abortion Federation, an abortion rights group, said. “It clearly demonstrates the inherent danger of empowering biased advocacy groups to impanel a grand jury.”

Normally, prosecutors decide whether to convene a grand jury to investigate something and bring charges.

Under the Kansas law, enacted during the Gilded Age and the nation’s great railroad boom to curb political corruption, the people can force an investigation if they collect signatures from a certain percentage of voters in a county. In small counties, that can be a few hundred signatures; in Wichita’s Sedgwick County, about 4,000.

Five other states provide for citizen-petitioned grand juries: Oklahoma, New Mexico, North Dakota, Nebraska, and Nevada, according to a Tiller attorney.

So far, no other state appears to have used the process to pursue a social and moral agenda as extensively as Kansas, which is attacking not just abortion, but pornography.