"In particular, his comment 'all this sex is beginning to get me horny' was inappropriate and inimical to the dignity of court proceedings," Kay said.
"Mr Lynch was justified in criticising it. However, I do not believe that it damaged the defence or had the potential to undermine the safety of the conviction."
Smith-Williams was sentenced to 35 years in prison last October after he was found guilty by a majority verdict.
A 29-year-old father of one was shot dead in February 2011 in Somerset, Bermuda.
A witness for the Crown told the court that Smith-Williams confessed his involvement in the killing to him and admitted that he had driven the getaway motorbike, Daily Mail reports.