One day before Martha Stewart was scheduled to arrive at a West Virginia federal prison to serve her five-month sentence, a federal jury in New York on Thursday acquitted a witness in Ms. Stewart’s high-profile trial for perjury.

Larry Stewart, a U.S. Secret Service agent and handwriting expert who is of no relation to Martha Stewart, faced 10 years on each of two counts of perjury related to testimony he provided during Ms. Stewart’s trial about a worksheet that prosecutors charged was illustrative of Ms. Stewart’s effort to conceal a suspicious stock sale in 2001.

In this most recent trial, federal prosecutors alleged that Mr. Stewart lied about having examined the documents himself.

The development comes as Ms. Stewart prepares to enter a women’s federal prison in Alderson, W. Va., to serve a five-month sentence for lying to investigators about that stock sale. Following her time in prison, Ms. Stewart will serve five months of house arrest, during which time she can leave her home only to run errands and go to work.

Ms. Stewart has indicated that despite going to prison, she will continue to seek to overturn her conviction.