{c{S}}

begin{filecontents*}{jobname.bib}
@article{A,
  author={{c{S}}author, X.},
  title={Title},
  journal={Journal},
  date={2014},
}
@article{B,
  author={Şuthor, X.},
  title={Title},
  journal={Journal},
  date={2014},
}
@article{C,
  author={Cauthor, X.},
  title={Title},
  journal={Journal},
  date={2014},
}
@article{D,
  author={Dauthor, X.},
  title={Title},
  journal={Journal},
  date={2014},
}
end{filecontents*}
documentclass{article}
usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}
usepackage{biblatex}
usepackage{csquotes}

addbibresource{jobname.bib}

begin{document}
cite{A}, cite{B}, cite{C}, cite{D}.

printbibliography
end{document}