The four-year-old has threatened to claim a good race but as a backmarker she has often been unlucky.
From a good draw on Saturday, Tommy Berry was able to position Subpoenaed ($5) closer in the run and she charged home to take out the 1400m race by 1-1/4 lengths over Emeralds ($15) with Jen Rules ($21) third.
Waller tried Subpoenaed over a middle-distance in the autumn but said he had finally figured out she was a sprinter-miler.
“She gives you the impression because she comes from behind that she will get further but it is not the case with her,” Waller said.
“She likes to be left alone early to find her feet and find her rhythm.
“There was good speed on and the barrier draw helped us be a little bit closer.”
Waller confirmed Subpoenaed would have her next start in the Silver Eagle with the Golden Eagle her ultimate target.
The premier trainer also saddled up favourite Haut Brion Her, who finished seventh, and he said she had to do too much work in the early stages.
A first up winner in Melbourne, I Am Superman found himself back in Sydney after he failed to get a start in last week’s Sir Rupert Clarke Stakes.
But he won’t be hanging around with Snowden confirming the horse would be back on the road to Victoria for a shot at the Toorak Handicap (1600m) at Caulfield in two weeks.
“We really wanted to win today to make sure we got into the Toorak. The Epsom is a little bit too strong on paper for him I feel,” Snowden said.
“We were devastated when we didn’t get a run in the Rupert Clarke last weekend. We thought he would be very effective.
“They were the races we wanted to be targeting, those Group One handicaps.”
I Am Superman ($4.60 fav) scored by 1-1/4 lengths over Riodini ($4.80) with Looks Like Elvis ($4.80) a close third.