Letter carrier Debbie Larson delivered mail to Deanna Cook's home between 10:30 and 10:40 a.m. on the day Cook was killed.
Larson said she saw Cook and Patrick walking down the street, but will not positively I.D. Patrick.
"I'm not scared, just apprehensive," said Larson.
Patrick has been charged with the vicious murder of ex-wife Deanna Cook. On Monday, Patrick pleaded not guilty to her strangulation death.
Larson's wavering testimony from what she said in August 2012 has left prosecutors frustrated.
Another witness, Dennis Williams, said that he saw Patrick at Cook's home the day she was killed.
The defense is now focusing on a toxicologist's report that revealed 0.20 milligrams of PCP in Cook's body.
Cook also had a BAC of 0.099, which the defense says could cause death, but could also be a result of the body's natural decomposition process.
Crime scene photos revealed Cook's body face down in the bathtub.
The gruesome sight of her bloated body and peeling skin sent many rushing from the courtroom crying.
Patrick watched the photos with no expression.