How to use "motive" in a sentence

There was also no obvious motive, such as robbery

The Ripper murders were the first of a new kind of crime: serial killings, savage, without an obvious motive, no clues, and very difficult to solve.

For me the important things are the character and the motive."

"So what about characters and motive?" he continues.

"So what's the motive?" Michael asks.

"But what about the woman's motive?" Michael asks.

But he could find no evidence and no motive.