The defence has argued that Chauvin did what he was trained to do and that Mr Floyd's death was not caused by the officer's knee, as prosecutors contend, but by Mr Floyd's illegal drug use, heart disease, high blood pressure and the adrenaline flowing through his body.
Another witness on Wednesday broke down in sobs on the stand as he watched police bodycam footage of Mr Floyd pleading for his mother during his arrest.
Day three concluded in the murder trial for former Minneapolis police officer Derek Chauvin.
Chauvin continued to kneel on Floyd while fellow Officer Tou Thao held back about 15 onlookers, even when Hansen identified herself as a firefighter and pleaded repeatedly to check Floyd's pulse, according to witnesses and bystander video.
Mr Martin said he initially planned to just put the bill on his own "tab" but then second-guessed himself and told a manager, who sent him outside to ask Mr Floyd to return to the store.
Lane also asked twice if the officers should roll Floyd on his side, and later said he thinks Floyd is passing out.
"If I would've just not tooken the bill, this could've been avoided", Mr Martin lamented, joining the burgeoning list of witnesses who expressed a sense of helplessness and lingering guilt over Floyd's death.
Martin said he immediately believed the $20 bill was fake. "I thought I'd be doing him a favor".
He said he had considered letting the shop deduct it from his wages instead of confronting Mr Floyd, but then chose to tell his manager.
Mr Martin and co-workers went outside to a vehicle where Mr Floyd was sitting with two other people but they refused to return to the store and the manager called the police. "He did seem high".
As McMillian cried, Chauvin and his defense attorney, Eric Nelson, could be seen writing down notes. He told the court Mr Chauvin had used a risky technique called a "blood choke" and was moving his knee back and forth to increase the pressure on Mr Floyd's back and neck.
Martin testified Wednesday that he watched Floyd's arrest outside with "disbelief - and guilt".
Mr Martin said he left the store again when he heard "yelling and screaming" outside.
In the footage disclosed publicly for the first time, Floyd ambled about Cup Foods for several minutes and appeared fidgety at times while chatting with others inside as Christopher Martin, a clerk in the store back then, explained in testimony what was being shown.
Also testifying on Wednesday was Charles McMillian, 61, who said he was driving by that day and stopped to see what was going on because he is "just nosy".
"Why did you feel the need to talk to Mr. Chauvin?" prosecutor Erin Eldridge asked McMillian, who earlier needed a break to push aside to tearful grief recounting that night.
At one point during his testimony, McMillan broke down sobbing, dropped his head, and removed his glasses to wipe tears from his eyes after prosecutors played the video of police putting Floyd in the auto.
"I felt helpless", Mr McMillian said.
Chauvin, a 19-year veteran of the police force, faces up to 40 years in prison if convicted of the most serious charge-second-degree murder.
Prosecutors are seeking to demonstrate to the jury that Mr Chauvin had no justification for using a risky neck restraint on a compliant Mr Floyd.
The trial is expected to last about a month.