FARMINGTON -- Fingernails with DNA.

Footprints in the snow.

Fingerprints on a milk glass.

Forensic-science techniques were at the forefront of testimony Thursday on the fourth day of the murder trial of Thomas H. Mitchell Jr. in Franklin County Superior Court.

Three forensic scientists working at the Maine State Police Crime Laboratory -- a biologist, a chemist and a latent-print analyst -- showed jurors how they did the work that led to the 2006 indictment of Mitchell in the Jan. 6, 1983, slaying of Judith L. Flagg in her Fayette home.

Cathy MacMillan, who conducts DNA analysis in that lab, used a wooden pointer to direct jurors through a PowerPoint presentation on how DNA profiles are determined.

Forensic DNA is used to show a relationship between victim, suspect and crime scene, she said.

"No two people have same DNA profile unless you have an identical twin," MacMillan said.

If 13 areas match 13 areas, the match is called "identity," she said.

DNA obtained from Flagg's right hand fingernails showed a full DNA profile from both Judith Flagg and Mitchell, MacMillan said.

Mitchell's attorneys are challenging the handling and storage of the material, claiming the samples of Mitchell's DNA cannot be connected to the Flagg case during the years the case had gone cold.

The trial continues today.