unfortunately you won't able to find how this process was ran. Here is a short description
for defunct process:
"Defunct — One that has terminated (either because it has been killed
by a signal or because it has called exit()) and whose parent process has not yet received
notification of its termination by executing (some form of) the wait() system call"
Also it is called "zombie" process. As you understand it is already terminated process,
it doesn't consume any resources but still exists in kernel table list