That doesn't make it reasonably 50/50, because you do have other information. Maybe you don't have specific stats at your fingertips, but you absolutely have information that would allow you to adjust your starting position on this.
First off, we all know that immigrants are a minority within the US, and illegal immigrants an even smaller minority. So right off the top, that reduces the likelihood that any give random criminal is an illegal immigrant. I don't have specific numbers, but I'd say it's more like 10% chance that a random criminal is here illegally.
But wait - there's more. We can reasonably surmise that the criminal in question is of hispanic descent, based on name and photo. And since we know that there's a higher prevalence of illegal immigrants within the subset of the US population that has hispanic heritage, that should nudge the likelihood up a bit. IMO I wouldn't move it to any higher than a 20% chance.
We also, however, know that the crime occurred in Los Angeles. And whether you want to acknowledge it or not, California in general and LA county in particular have taken a policy position of acting as a "sanctuary" for illegal immigrants, with a very low propensity to either report or deport. That then creates a higher likelihood of any given person (regardless of ethnicity) in Cali being illegal. But still a minority.
All of these things taken together would nudge the starting point of a reasonable person with a moderate understanding of statistics. If I'm feeling very aggressive toward reducing illegal immigration, I might be inclined to go as high as 40% likelihood of a random hispanic criminal in LA being illegal. If I'm feeling conservative, I might go as low as 25% chance.
Either way, it's not reasonably 50/50.