If all the below statement are true

1. Gianni was either in Italy or France in 1997.
2. If Gianni did not kill Versace, then Hilton must have killed him.
3. If Versace died of suffocation, then either Gianni killed him or Versace committed suicide.
4. If Gianni was in Italy in 1997, then Gianni did not kill Versace.
5. Versace died of suffocation, but he did not kill himself.

Who killed Versace and where was Gianni in 1997 ?

Statement Problem

Gianni was in France in 1997 & he killed Versace.

Versace died of suffocation=>This information should lead you to statement #3 next. From here you should gather that Gianni killed Versace.
Thus leading to statement #4, Gianni was in France in 1997.