Why does Walmart keep changing its story about worker fired for redeeming empty cans?

Remember the Walmart worker whose story went viral after he was fired, apparently for redeeming empty cans he cleaned up from Walmart property? That didn’t look so good for Walmart, so the retail giant came up with another explanation for Thomas Smith’s firing … and then another explanation, and another:

After Smith signed a statement admitting to redeeming the cans, a Walmart spokesman said his firing was actually for theft inside the store, and gross misconduct, and that redeeming the cans had nothing to do with it. But that wasn't the last time the story would change.

The Albany Times Union reported that Aaron Mullins, a spokesman for Walmart, later told The Washington Post that Smith was fired for redeeming bottles submitted by customers to the customer service desk. But the customer service desk does not manage empty bottle returns.

Now, Michelle Malashock with Walmart's executive communications department claims Smith was fired because he "did not disclose certain serious criminal convictions during the application process."

Smith, who is on probation, says he included his 2002 robbery conviction on his job application, and the statement Walmart initially made him sign when he was fired talks about the cans he redeemed but didn’t say anything about his criminal record. In other words: Walmart is in full ass-covering mode.