A district court acquitted a former assistant store manager - who said she had taken home certain items by mistake - of theft, and made clear it was for prosecutors to show that she intended to steal, not for her to prove her innocence.

Ms Jenn Lye, 46, was alleged to have stolen three items worth $500 from the Valentino store in Ion Orchard in 2014 while employed there, but District Judge John Ng found she could have taken the items home by mistake, after reviewing the case.

"The prosecution had not been able to prove beyond a reasonable doubt that ( Ms Lye) had removed the items from the store dishonestly," he said in grounds read out on Tuesday following a four-day trial.

Ms Lye, defended by lawyer Peter Ong Lip Cheng, claimed that she had taken two silver charms and a leather key holder out of the store "accidentally" from her locker when she was packing up, as she was going to resign. These items had been temporarily placed in her locker during a time when the company was upgrading to a new accounting system which involved the migration of certain data.

The prosecution had relied on a statement Ms Lye had given to the investigating officer (IO) to show her dishonest intention. But the judge pointed out that her statement had to be checked against the IO's testimony in court on what transpired and how Ms Lye came across to the IO at the time.

Ms Lye had told him during the probe that she had accidentally taken the items home, but after a series of questions she said "yes" when he asked her if she had "deliberately" taken the items.

Asked why she made the sudden change in response, she answered: "The truth is I deliberately took it home because I do not know how to answer the why, why, why." When pressed further, she replied: "I just want to admit to the mistake because the items are in my house. There is nothing much I can say."

The judge, noting that the IO "was careful in his recording and for that Ms Lye can be grateful", said the "why, why, why" reflected her frustration. The judge added that if she had wanted to steal, "the easiest thing to do would be to feign ignorance as to the whereabouts of the items". She also promptly returned the items to the store after finding them at home, he pointed out. Given the various doubts raised, he said it was unsafe to find her guilty.