On the way home from work, I grabbed the pile of comics from my store and read Identity Crisis #6 (of 7) at the stoplights. I now know who did it.
It was Jean Loring. She had access to Ray's technology. She has survived being shrunken using that technology. Her phone was off the hook in issue #1 while Sue was being murdered so she could get back on the phone lines. Her "attempted murderer" left her hanging from a noose so Ray could rescue her. And then she arranged the frame with the Calculator on some other criminal.
Why? She wants Ray back. And he wouldn't come back to her under any normal circumstances, since she was the one guilty of infidelity. But these circumstances are nothing like normal.