Starter motor not starting

Ok so I haven't been using the Caddy too much but starting it every so often. I noticed the past few times it was slow at turning over but assumed it must be the battery. Today I turned the key and nothing so I put jump leads on and still nothing> checked the battery and holds 13v so that seems about right. I twatted the starter motor and it made a bit of a noise while I turned the key. Then there was smoke coming from the starter motor area. Was it always the starter?

I suspect two possibilities.

Bad Frame to engine Ground, or a fried starter, and or both.

Take the starter out and have it tested, then go from there, I would also say off the top of my head to replace the bushing if you replace the starter.

Also, I had tried to start it from another car with jump leads so assume this rules out the battery?

Pretty much, doesn't rule out bad cables, but if it was smoking it is probably toast.