If someone says,
“A certain person cohabited with my wife,” (a sin for which both parties
are liable to the death penalty,) he and another witness can join in
testifying against the adulterer, but not against the adulteress. A man
is considered a relative of his wife, and a relative cannot testify.
Even though he testifies about one act, we believe him regarding the
adulterer, but not regarding his wife. This principle is called "we
split the testimony".
Cases of lashes are decided by three judges: "...And they (the judges) shall
judge them..." gives two judges as the minimal number of “they,” and
since a court consisting of an even number of judges is not acceptable,
one more judge is added. Rabbi Ishmael requires twenty three judges,
based on the use of the same word "evildoer" in "...evildoer liable to lashes..."
and in "...who is an
evildoer to die."
Art: Gustav Klimt- The Kiss 