Aaron Hernandez Fiancee Cites Infidelity, Says She Dumped Box Prosecutors Believe May Have Held Murder Weapon

— -- Aaron Hernandez's fiancee, Shayanna Jenkins, told the jury at his murder trial in Fall River, Massachusetts, today that Hernandez instructed her to remove a mystery box from their home -- a home they continued to share, she added, despite her suspicions he had been unfaithful to her.

Hernandez told her to "go downstairs in our storage and remove a box from our home" on the afternoon after Odin Lloyd was killed, Jenkins testified, and she described how she disposed of it, ultimately dumping it in a "random dumpster."

Hernandez, 25, is on trial for Lloyd's murder and has pleaded not guilty. Prosecutors believe the box may have contained the murder weapon, which has never been found, or other evidence.

Jenkins, 25, cried on the stand during talk of Hernandez's possible infidelity. She said she saw suspicious phone messages and stayed at a location away from their home for a few weeks. Ultimately, she added, the couple decided to work through their problems and continue the relationship. Jenkins said her definition of infidelity includes sexual intercourse, and she wasn't sure that happened.

Hernandez, a former New England Patriots football player, is accused of orchestrating Lloyd's slaying June 17, 2013. Prosecutors say Hernandez and two other men picked up Lloyd from his house and brought him to an industrial park near the Patriots' Gillette Stadium.

Surveillance video played for the jury today showed Jenkins going into the basement. Video previously played for the jury showed Jenkins removing a garbage bag from their home with what appeared to be a box inside.

"Did he indicate what was in the box?" prosecutor Patrick Bomberg asked Jenkins today.

"No," she answered. She added, "His tone, I believe, was normal," but she recalled him saying moving the box was "important."

Jenkins said the box was not sealed, and contained smaller boxes with cardboard on top of them. She said she put the box "in a trash bag" with her baby daughter's clothing "so nothing was exposed."

"I wasn't necessarily hiding it," she said. "It was just natural instinct."

Jenkins said Hernandez did not talk about the contents of the box and she did not ask.

Later, under cross-examination by Hernandez's lawyer, Jenkins said the box had a "skunky smell," and she suspected it might contain marijuana.

Jenkins estimated that the bag with the box in it weighed about 35 or 40 pounds. Surveillance video played in court showed Jenkins putting the bag in the trunk of a car and driving away. She testified she disposed of the box in a trash bin, but doesn't recall where.

"I found a random dumpster," she said.

She added she was nervous about "everything going on."

Jenkins has pleaded not guilty to a perjury charge for earlier testimony to a grand jury in the case, according to The Associated Press. In contrast to her testimony today, the AP reported, Jenkins said during her grand jury testimony that nobody told her to remove the box.

Jenkins was granted immunity in February.

Jenkins and Hernandez were high school sweethearts and have a 2-year-old daughter together.

ABC News' Ryan Smith and Alexa Pozniak contributed to this report.