In reply to:
how would you determine if you have/had a parent who is a psychopath?
As you have no contact with your father, one course - psychiatric diagnosis - is irrelevant.
There is no simple answer, and it is not a question anybody can answer for you.
The only thing you can do is learn as much about the subject as you can and then ask the the question of yourself.
If you intend to seriously address this question, there are a couple of books that I reccomend you buy (available from Amazon)
"Without Conscience" by Robert Hare
"The Sociopath Next Door" by Martha Stout
Its a complex and evolving field in which there is both a deficit of basic research - schizophrenia for example has been far more heavily investigated than personality disorder - and where there is a wide variety of opinion.
Theres a fair ammount of info on the web - very variable in quiality and a lot of it just rehashing other sources. Search terms to use at Google "Psychopath" " Sociopath" and "Antisocial Personality Disorder"
As you have had no contact with your father for 19 years, the qustion of whether he does or does not deserve the label "Psychopath" would appear to be academic. You know WHO he was because you grew up with him, and any conclusion you come to regarding psychopathy will have no practical benefit for you now.
In contrast to your situation, for many people who suspect that the person they are in a relationship with might be psychopathic, the correct answer to the question can have profound implications to the future course of their lives - if they come to the conclusion that their lover / husband / business partner is a psychopath then there is only one possible course of action - the relationship must be terminated, as there is only ever ONE outcome of extended contact with a psychopath: damage - any combination of emotional, physical and financial. A relationship with a psychopath cannot be 'fixed' and the psychopath will never change - thinking otherwise is a trap many people fall into.
Feel free to ignore this if you feel Im being nosy, but why do you want to know? Does it matter at this stage what label you place on you father? Will it help you in some way? (this is just me being curious)
Exactly WHY psychopaths become psychopaths in the first place is very open to question, so just being able to stick a label with an agreed definition on your dad will not tell you a great deal about WHY he BECAME the way he was.
In my opinion the origin of psychopathy is a complex interplay of nature (genetics) and nuture (environmental influences from all sources - parents, siblings wider society) which results in the failure to establish a child-parent bond at a very early age, and then a subsequent failure of the normal process of socialisation - and I repeat thats just my own feeling on the subject.
The trouble is this is also one of the areas about which least is known. I also think that there are likely to be a variety of 'routes' to psychopathy - no single simple cause for the emotional deficit (inablity to process and react in a normal emotional way to external stimuli - the psychopath does not emotionally 'feel' the difference between a photograph of a dieing baby and that of a Duracell battery) which undelies the syndrome - the observed cluster of behaviours, character and lifestyle traits which together are are the outer signs of 'psychopathy'. Even physical damage to the pre-frontal cortex of the brain (e.g. bullet or car crash or infection) will do - sometimes a radical change of character from 'normal' to that of a psychopath will result.