The Chicago Manual of Style no longer imposes sentence-style capitalization on titles. In response to this change the biblatex-chicago author moved sentence case title formatting from the default authordate style to a new style call authordate-trad. So to obtain an English bibliography with sentence-cased titles load babel and biblatex with the option settings:
\usepackage[german,british]{babel}
\usepackage[authordate-trad,babel=hyphen]{biblatex-chicago}
For a multilingual bibliography incorporating both English and German strings, change the setting babel=hyphen to babel=other. Note that you might need to protect some words in titles from down-casing. For example:
title = {Darwinizing Culture: {The} Status of Memetics as a Science},
Alternatively you can use the subtitle field:
title = {Darwinizing Culture},
subtitle = {The Status of Memetics as a Science},
Also note that sentence case is applied only under the language modules specified in \DeclareCaseLangs. By default:
\DeclareCaseLangs{%
american,british,canadian,english,australian,newzealand,
USenglish,UKenglish}
To include german in this list, add the following to your preamble:
\DeclareCaseLangs*{german}
Best Answer
\dq ashould work. Note also that proper quotation marks would bei.e. "quotation backtick" and "quotation apostrophe". (Also see the csquotes package.)