Nixon's handling of the tapes during this period is astonishing -- if, perhaps, understandable given the predicament he was in. His custody of this evidence (already subpoenaed, with the court fight continuing) was personal. Haldeman still had access during part of this time; now, on September 29, he, the tapes covered by the court case, and Rose Mary Woods (his longtime and loyal secretary) went to Camp David so she could start, with little assistance, preparing partial transcripts.
They then discover -- apparently, they didn't realize it until that weekend -- that two of the nine tapes the court had asked for didn't exist, thanks to glitches or holes in the taping system. They also discover how difficult the job actually is; Woods spent 29 hours that weekend, running the tapes over and over to try to make out as much as she could, without finishing the first one.
As Emery notes, Woods was working with the original tapes; no copies had been made, or any other safety precautions.
Of course, Nixon could have turned the tapes over to his lawyers...but clearly Nixon trusted Woods with the whole truth much more than he trusted his lawyers, at least until he could learn what he was up against.