Simpson, who faces a two-year ban if found guilty of a doping violation, testified in front of a three-member panel for over three hours and said a supplement provided by her Canadian trainer was responsible for her positive test.
Simpson was one of five Jamaicans to test positive at last June's national championships. Both she and former world 100 record holder Asafa Powell returned adverse findings for the banned substance oxilofrine.
The Olympic 4x100 relay silver medallist said she was not familiar with one of the five supplements given to her but that nothing on the bottle of Epiphany D1 appeared during her online search of the World Anti-Doping Agency's banned list.
"No alarm bell. No red flag," told the panel.
But a lawyer for the Jamaica Anti-Doping Commission said that there is no evidence to suggest oxilofrine is contained in Epiphany D1 and that Simpson was negligent not to have consulted a doctor.
The lawyer also said Simpson did not disclose that she was using Epiphany D1 along with three of the other four supplements provided to her by her trainer.
But Simpson, who said they were new additions to her regimen and that she could not recall their names at the times, insisted she was "not a cheat."
The hearing resumes on Wednesday.