It took a Spokane County Superior Court jury less than a day to find Clay Starbuck guilty of murdering his ex-wife, Chanin, in her Deer Park home in December 2011.
Starbuck, who took the stand in his own defense on May 29, faces up to life in prison.
His defense team said they would appeal the verdict.
The jury, which heard closing arguments from both sides and final deliberation instructions on Monday, reached its decision late Tuesday evening.
During the deliberations, the jury requested to hear a 34-second 911 call from Chanin Starbuck's cellphone on the day investigators believed she died. While no voices could be heard on the phone call, prosecutors claim gurgling noises could heard before the cellphone call ended.
Prosecutors theorize that Starbuck killed his ex-wife to get out of the almost $9,000 in back child support payments he owed her.