If convicted, Brett Hankison could spend the rest of his life in prison.
He has pleaded not guilty to the charges and was acquitted on separate state charges last year.
Ms Taylor's killing, as police officers tried to execute a search warrant on her Kentucky apartment, sparked rallies against racial injustice across the US.
The nine-day trial has revolved around whether or not officers should shoot when they have not clearly identified their target.
According to Louisville authorities, another detective, Myles Cosgrove, fired the fatal shot that struck Ms Taylor, a 26-year-old black woman, but Mr Hankison fired 10 shots during the chaotic "no-knock" raid.
None of those bullets struck anyone but some rounds strayed into an adjoining apartment where a couple and their child lived.
Prosecutors have said that Mr Hankison endangered Ms Taylor, her boyfriend and the neighbours by needlessly using excessive force.
Officers are charged with protecting human life, they argued, and the former detective had "dishonoured" his colleagues by "firing blindly".
But defence lawyers asked jurors to consider "the chaos he was surrounded with" and the fact that he "reacted by trying to protect the lives of his fellow officers and himself".
How he responded, they claimed, was "reasonable, not criminal".
Taking the stand, Mr Hankison admitted that he could not see a target through the covered windows or sliding door of Ms Taylor's apartment but said he saw muzzle flashes from gunfire and believed a shootout was taking place.
Jurors spent Tuesday deliberating, at one point asking if they could separate Mr Hankison's level of force from how it was used.
The judge asked them to re-read the jury instructions in the case.
In March 2022, a Kentucky state jury spent about three hours in deliberation before finding Mr Hankison not guilty of three counts of felony wanton endangerment during the incident.
But three other former officers involved with the raid have been charged in separate federal cases.
One of them, Kelly Goodlett, has pleaded guilty and is expected to testify against the others, Joshua Jaynes and Kyle Meany, in their joint trial next year.
The raid was part of a sprawling drug investigation, but no drugs were found in Ms Taylor's home.
In December, Ms Taylor's boyfriend, Kenneth Walker, received a $2m (Â£1.7m) settlement from the city.
The death of Ms Taylor, along with that of Ahmaud Arbery in Georgia and George Floyd in Minnesota, sparked widespread anti-racism protests across the country.
Jurors in the federal trial of the ex-police detective accused of violating Breonna Taylor's civil rights have begun deliberating for a third day.