Scientific or lay audience? That's the wrong question
When I teach my presentation course one of the first questions I get is whether we are preparing a presentation for a scientific or a lay audience. This question is too simplistic.
I attend many scientific seminars at Stanford University and typically the audience is varied. There are audience members with expertise in the speaker's specialized sub-discipline, with expertise in related disciplines, and scientists from very different disciplines who may have techniques relevant to the speaker's research. For example, one goal at the Stanford Cancer Institute is to engage Stanford's outstanding bioengineers in cancer research.
In other words the typical scientific audience consists of members with a wide range of expertise. For example, a job talk will contain members from your sub-disciplines as well as department chairs who have little background in your work, but will ultimately decide if you get hired.
Equally important, you probably won't know who is going to show up.
Similarly lay audiences can vary. Give a presentation to a potential CEO donor from a tech company and he/she may not know your science, but they will want a hard-nosed analytical story. Other lay audiences may just want to be "wowed."
So the audience is varied and you don't know how varied. See the previous "tip" for a strategy for coping with this uncertainty.