I clicked the link and here is the statistical basis for this article
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While no government agencies specifically track crimes by illegal aliens, there have been some efforts to quantify the loss. Last December, Mac Johnson set out to investigate the number of homicides perpetrated by illegal aliens. Since the federal government would not provide any useful information, he contacted all 50 statehouses. Three months later, he had fewer than a dozen responses. Only one state, Vermont, provided any useful information.
He then set out to statistically estimate the number of murders by illegal aliens based on available crime data and conservative estimates of the actually number of illegal aliens in the country – which, of course, nobody really knows.
He found that between 1,806 and 2,510 people in the U.S. are murdered annually by illegal aliens. If he's right, that would represent between 11 percent and 15 percent of all murders in the U.S.
In one study of a sample 55,000 illegal immigrants serving prison sentences in the U.S., it was discovered that they are responsible for over 400,000 arrests and over 700,000 felony crimes.