The first question to ask about the palmprint is this:  do we know that this print is the print of the perpetrator?  In other words, does *not* matching this print exclude you from consideration?  Does matching this print mean you are the perpetrator?

Is the palm print the litmus test, or is it something else?

The article below from 2004 reports on Thomas Corscadden's palm print being compared to the one found on the car, and at face value you might read that and assume that since his print does not match the print on the car, he therefore cannot be the guilty party....but that may not be the case.  To my understanding, Mason City LE has not stated that the print certainly MUST be that of the perpetrator.  It might, for example, be the palm print of someone who opened (or closed) her car door at any point in the then-recent past for any number of innocuous reasons.  By way of example:  let's assume someone walked her to her car following the golf tournament.  Let's assume this person was a gentleman and opened and then closed her car door for her.  Next time you close a car door, notice what part of your hand makes contact with the door? If that is the case, then the print doesn't carry much weight at all; it simply means that if you DO match it, you are someone LE wants to talk to further.  And if you match it and you have no legitimate reason for having been anywhere near that car then you are REALLY someone LE wants to talk to further.  

https://www.postbulletin.com/austin-edition-austin-man-s-prints-not-linked-to-huisentruit/article_1ff3db8c-ff05-5deb-ae09-a5e604911bda.html

I'd be very surprised if LE truly gives this palm print a lot of weight, since they may not be able to determine how or when it was imprinted.  It is likely viewed as an additional qualifier of a suspect but I doubt it is viewed as a disqualifier.

To your question:  it's a good one.  It's a good question because we see press coverage on this particular match attempt with Corscadden, but we don't see any with regard to Jackson.  This leads me to believe that LE did not run a palm print match on Jackson.  The reasons for this are unknown, but it follows that they must have ruled him out based on some other criteria and therefore did not see the wisdom in doing this analysis.  Another very real consideration would be that the palm print itself was lost and is therefore no longer available for matching (this happens, a lot more than you would think), and of course it is possible that a palm print comparison was made with Jackson's prints but for whatever reason was not revealed to the media.

The real question, in my mind, is not *if* Jackson's print was compared to the one on the car, but *why* LE has stated that he is not a person of interest in this case.  The statements I've seen from the Mason City PD re: Jackson is that he simply isn't connected in any way to the crime.  I'd love to hear more of an explanation, as he seems to check a lot of boxes for the type of person who may be involved, and we have some reports that a witness has stated that Jackson was seen talking to Jodi in the weeks prior to the abduction.