The staging itself is sinister.
There were shards found around the paint tote in the basement. But like much in this case, it can't be determined (at least from a forensic aspect) of when they were left.
We do know that housekeeper LHP said that Patsy told her to remove the paint tote from the Butler's pantry near the kitchen, where she had been keeping it.
This was Dec. 23, the day of the Patsy's Christmas party, and LHP was there to help her clean and prepare for the party. Patsy said she wanted to put a coat rack in the Butler's pantry so she told LHP to move the paint tote to the basement. So the shards had to have been left between Dec. 23 and 26th. I can't imagine it being done any time other than the 26th BUT-
BR was known to whittle with his Swiss Army knife all over the house, and whittle whatever he could. LHP was always complaining to Patsy about it, and Patsy said there wasn't much she could so about it other than take the knife away. LHP did take it away, and hid it in the cabinets near the 2nd floor laundry area, outside the kid's bedrooms. LHO said only Patsy knew where it was hidden, but BR may have found it or Patsy may have told him where it was.
I can't imagine BR deciding to break the brush to whittle just before his sister was strangled with it, though he may have done it before this happened, and the "handle" may simply have been used because it WAS just a broken piece and not broken just to make the garrote. Maybe someone should have searched BR;s room for the missing piece. He may have taken it to whittle, and the actual breaking of the brush may have nothing to do with the crime.