Fla. Std. Jury Instr. (Civ.) 420.5

a. Legal cause generally:

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 conduct, 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] negligence need not be the only cause. 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 negligence contributes substantially to producing such [loss] [injury] [or] [damage].

c. Intervening cause:

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

*[In order to be regarded as a legal cause of [loss] [injury] [or] [damage], negligence need not be its only cause.] 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 negligence occurs if [such other cause was itself reasonably foreseeable and the negligence contributes substantially to producing such [loss] [injury] [or] [damage]] [or] [the resulting [loss] [injury] [or] [damage] was a reasonably foreseeable consequence of the negligence and the negligence contributes substantially to producing it].