Let
R be an
n!-torsion free semiprime ring with involution
* and with extended centroid
C, where
n\,>\,1 is a positive integer. We characterize
a\,\in \,K, the Lie algebra of skew elements in
R, satisfying
{{(\text{a}{{\text{d}}_{a}})}^{n}}\,=\,0 on
K. This generalizes both Martindale and Miers’ theorem and the theorem of Brox et al. In order to prove it we first prove that if
a,\,b\,\in \,R satisfy
{{(\text{a}{{\text{d}}_{a}})}^{n}}\,=\,\text{a}{{\text{d}}_{b}} on
R, where either
n is even or
b\,=\,0, then
{{(a\,-\,\lambda )}^{[(n+1)/2]}}\,=\,0 for some
\lambda \,\in \,C.