What facts will reduce an intentional killing from murder to manslaughter when based on heat of passion?

In a recent decision, we discussed what facts will reduce an intentional killing from murder to manslaughter, when based on heat of passion: "An intentional, unlawful homicide is `upon a sudden quarrel or heat of passion' ( 192(a)), and is thus voluntary manslaughter (ibid.), if the killer's reason was actually obscured as the result of a strong passion aroused by a `provocation' sufficient to cause an `"ordinary [person] of average disposition ... to act rashly or without due deliberation and reflection, and from this passion rather than judgment."'" (People v. Breverman (1998) 19 Cal.4th 142, 163, 77 Cal.Rptr.2d 870, 960 P.2d 1094.) No specific type of provocation is required, and "the passion aroused need not be anger or rage, but can be any `"`[v]iolent, intense, high-wrought or enthusiastic emotion'"' [citations] other than revenge [citation]." (Ibid.) Thus, a person who intentionally kills as a result of provocation, that is, "upon a sudden quarrel or heat of passion," lacks malice and is guilty not of murder but of the lesser offense of voluntary manslaughter.