Evolution deniers trust the results from paternity testing in humans. The same method is used to determine evolutionary relationships.

This is from The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution by Sean B. Carroll:

Fortunately, there is, however, an altogether new way of deciphering species' relationships. It also relies on DNA, but rather than being based on the degree of sequence similarity, it looks for the presence and absence of certain landmarks in specific places in species DNA. These landmarks are produced by accidental insertions of junk DNA sequences near genes. Particular chunks of junk DNA, call long interspersed elements (LINES) and short interspersed elements (SINES), are very easy to detect. Once a SINE or LINE is inserted, there is no active mechanism for removing it. The insertion of these elements marks a gene in a species, and is then inherited by all species descended from it. They are really perfect tracers of genealogy. These insertion events are very rare; therefore, their presence in the same place in the DNA of two species can be explained only by the species sharing a common ancestor. The inheritance of variable markers in DNA is the same principle applied to paternity testing in humans. By surveying the distribution of a number of elements that arose at different times in different ancestors, biologists have sufficient forensic evidence to determine species' kinship beyond any doubt.