Fla. Std. Jury Instr. (Civ.) 403.12

a. Legal cause generally:

[A defect in a product] [Negligence] is a legal cause of [loss] [injury] [or] [damage] if it directly and in natural and continuous sequence produces or contributes substantially to producing such [loss] [injury] [or] [damage], so that it can reasonably be said that, but for the [defect] [negligence], the [loss] [injury] [or] [damage] would not have occurred.

b. Concurring cause:

In order to be regarded as a legal cause of [loss] [injury] [or] [damage], [a defect in a product] [negligence] need not be the only cause. [A defect in a product] [Negligence] may be a legal cause of [loss] [injury] [or] [damage] even though it operates in combination with [the act of another] [some natural cause] [or] [some other cause] if the [defect] [negligence] contributes substantially to producing such [loss] [injury] [or] [damage].

c. Intervening cause:

*Do not use the bracketed first sentence if this charge is preceded by the charge on concurring cause:

*[In order to be regarded as a legal cause of [loss] [injury] [or] [damage], [a defect in a product] [negligence] need not be its only cause.] [A defect in a product] [Negligence] may also be a legal cause of [loss] [injury] [or] [damage] even though it operates in combination with [the act of another] [some natural cause] [or] [some other cause] occurring after the [product defect] [negligence] occurs if such other cause was itself reasonably foreseeable and the [product defect] [negligence] contributes substantially to producing such [loss] [injury] [or] [damage] [or] [the resulting [loss] [injury] [or] [damage] was a reasonably foreseeable consequence of the [product defect] [negligence] and the [product defect] [negligence] contributes substantially to producing it].