Simpson and former 100 metres world record holder Asafa Powell, who also testified at Wednesday's hearing, returned adverse findings for the banned drug, oxilofrine, at June's Jamaican championships.
Both face two-year bans if found guilty of doping violations.
Two separate tests on a sealed bottle of "Epiphany D1", a supplement she was taking, showed the presence of banned drug oxilofrine, Professor Wayne McLaughlin of Caribbean Toxicology, a witness for Simpson, told the three-member Jamaica Anti Doping Disciplinary Panel.
McLaughlin noted, however, the drug was not listed on the label of ingredients of Epiphany D1.
But testing by HFL Sports Science-Informed Sports, showed conflicting results, according to documents submitted by Simpson's legal team.
One tested bottle, without an expiry date, showed the presence of oxilofrine, while a bottle with an expiry date, did not, the report from the Kentucky laboratory said.
A lawyer representing the Jamaican Anti-Doping Commision had told the hearing on Tuesday there was no evidence to suggest oxilofrine is contained in Epiphany D1.
Powell, who will have a similar hearing later this month, said he had been unaware the two sprinters were taking the same supplements, which were provided by Canadian physical therapist Chris Xureb.
"After we were notified of our positive test, we sat in my room (in Lignano, Italy) and spoke," Powell said. "That's when I found out we were taking the same things."
Simpson, testifying for a second day, told the panel she was unaware of published advisories from the International Association of Athletics Federations, the World Anti-Doping Agency and other anti doping organizations against using supplements.
Simpson's hearing will resume on Feb. 4.
Powell's is scheduled to begin on Jan. 14.
- Addiction & Substance Abuse
- Asafa Powell