Is it easier to lie when writing than speaking? Yep. Is it easier to lie when emailing than writing a letter? Yep.
…at least according to this blog post about some psychology tests done by Charles Naquin from DePaul University.
This is explained by moral disengagement framework, i.e.
“…people resolve guilt and responsibility for transgressing self-imposed moral standards is by distancing themselves psychologically from the consequences of their actions”.