Lara Keller told Queensland Health director-general Shaun Drummond that samples were being sent for amplification before 2018 in an email in June.
However, Ms Keller was informed 11 days later this was an issue, and the samples were supposed to go for concentration before amplification prior to 2018, an inquiry into the lab Brisbane heard on Tuesday.
Ms Keller says her email was based on the advice of scientist Dr Cathy Allen, who she said "took responsibility" for the mistake.
"I rely on Cathy to provide me with the scientific advice," Ms Keller told the inquiry.
"That is what I did and that is what I referred to the director-general in good faith at the time, based upon that advice."
Ms Keller said she had since spoken with the director-general, and explained that she had never intended to give incorrect information.
"It was never my intention to mislead them or give them the wrong information and I feel dreadful about the fact that that happened, because that's not me, I would never do that," she added.
"So, if you're saying, do I feel embarrassed? Of course I do."
Ms Keller told the inquiry on Monday she didn't understand issues raised by police about getting usable DNA profiles for cases from samples which contained less than two per cent DNA.
At their own request, police later sent some samples for further testing and almost a third produced usable DNA profiles.
When asked if she had any interest in the issue raised with her, she blamed time constraints.
"I don't believe that you have any knowledge of what goes on at FSS because if you did, you would know that I've got seven scientific disciplines to try and get my head around," Ms Keller said.
"I absolutely had the interest. Did I have the time? Possibly not.
"Would I go back and read all the textbooks now? Of course.
"It's what it is, I did my best."
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