The defense rested its case, The (Cleveland) Plain Dealer reported. Closing arguments were scheduled for Wednesday.
Sowell, 51, faces a long list of charges. After prosecutors rested Monday, Common Pleas Judge Dick Ambrose dismissed counts of felony murder and kidnapping involving one victim, reducing the number of counts to 83.
Sowell is also charged with attacking several women who managed to get away alive.
The defense list of potential witnesses included Cleveland Mayor Frank Jackson. His niece was a prosecution witness, testifying she was involved with Sowell for part of the time he was allegedly carrying out the killings.
Sowell could be sentenced to death if convicted.