[AC Question]

How can I detect spyware on my s3?

[B. Diddy]

Welcome to Android Central! What makes you think you have spyware?

Try installing various security/antivirus apps and running scans. If they come up empty and you still think you have spyware onboard, a surefire way is to do a factory reset and prevent the phone from automatically restoring (in Settings>Backup & Reset, uncheck "Automatically Restore" before the reset).