Three Chester County men already charged with a Coatesville murder have been indicted by a grand jury in a strategy aimed at preventing witness intimidation, officials said Wednesday.

Taking advantage of a recent change in state law, District Attorney Tom Hogan said he opted for a grand-jury proceeding rather than have witnesses appear at a preliminary hearing.

Hogan said a "stop snitching" culture, particularly well-entrenched in Coatesville, sometimes discourages witnesses from taking the stand.

The grand jury indicted Marquis Rayner, 23, Camren Horne, 20, and Dominique Lee, 20, who in March were charged with the home-invasion murder of Dominique Williams.

To date, Chester and Philadelphia are the only two counties that have taken advantage of a change in Pennsylvania law late last year that permits counties to indict by grand jury in cases in which witness intimidation is evident or likely.

In a grand jury proceeding, witnesses' testimony is secret, which may ease fear of testifying, Hogan said.

"In a preliminary hearing, you would be called as a preliminary witness, it would happen a week after the arrest, and everybody there knows who you are and what you said," Hogan said. "You paint a target on yourself."

Rayner, Horne, and Lee have been charged with homicide, robbery, conspiracy, and related offenses, all stemming from Williams' June 29, 2012, slaying.

According to court documents, the three men entered Williams' house wearing black T-shirts around their heads. One shot Williams immediately, shouting, "Where's it at?" Police said the three left with a jar holding marijuana, police said.

Police found the jar and one of the T-shirts near the house and linked Rayner to DNA found on the garment. Police said Horne later told a witness about his involvement with the slaying, saying that the three had planned only to rob the house but that one of the men had shot Williams. Lee's fingerprint was found on the stolen jar, police said.

Hogan would not say whether witness intimidation had occurred in the Williams case, and grand-jury proceedings are not matters of public record.

He did say that intimidation was an issue in Coatesville. Said Hogan, "There is a drug trade there and a long history of people intimidating witnesses."

Contact Aubrey Whelan at 610-313-8112, at awhelan@philly.com or on Twitter at @aubreyjwhelan.