From the article I linked above:
  • Steven Avery had purchased handcuffs and leg irons three weeks before Teresa went missing. The state claims Brendan Dassey admitted these items were used to restrain Teresa in Steven’s trailer.

Steven openly admitted in a Milwaukee Magazine article he did purchase these items, but he bought them to use with Jodi. And, unfortunately for the state, none of Teresa’s DNA was found on the leg irons or handcuffs, which seems very hard to believe if she really was shackled to Steven’s bed.