How did He get from Croatia to Washington state? How will his case worker get the rule out? There has to be a good argument for submitting people from other countries before actually submitting.
During the civil War in Croatia a number of people went 'missing', so it's not unfeasible that he somehow made his way out of Croatia, traveled across Europe and then made his way to the US using various ports with a false passport.
Perhaps he came across a large sum of money, or something of great value which he was able to use to fund his escape?
If Ilija was, (as shown in the picture on the Croatian missing persons website where he is shown wearing a uniform), an enlisted soldier then he may have been a deserter, which mean that leaving Croatia under the guise of a civilian refugee under a false name and with false papers would have been essential, as in times of war in most armies desertion is a crime punishable by death.
This would also explain the reason why he had chosen to commit suicide.
In the US after the 9/11 attacks (which were so close to the date of his suicide), it would have been obvious to any forward thinking person that obvious 'foreigners' would be subject to rigorous inspection of their identification, and if Ilija had been traveling under false identification then he knew that his real identity would soon be exposed and that he would, at best, be sent back to a place which he had no intentions of returning to, and at worst, there be imprisoned or perhaps, worse.
I'm basing these assumptions on the identical appearance of the men in these two images as a trained professional artist who has studied and reproduced in exact detail the minute details of the features of the human face countless times.
As far as a 'rule out' goes, I'm expecting that if Ilija Dukic was a military enlistee and, (as is standard when enlisting in the military), the records of his fingerprints still exist on file in Croatia then they might be able to compare those of his with those of 'Lyle's' by email, in which case I'm actually expecting an exact match.
Or, if Ilija still has living relatives in Croatia who actively searching for him, (which is highly likely, considering that someone must have notified the authorities that he is missing, hence his entry on the Croatian missing persons page), and the Croatian and US authorities see what I, and a number of other people are also seeing, in regard to the exact likenesses of these two men, (apart from an obvious pretty much exact age progression), then I'd imagine the Croatian officials might ask these relatives to submit a DNA sample to compare to that of 'Lyle', in which case I'm also not expecting a 'rule-out' either, I'm expecting a match.