It really won’t help him much , maybe manslaughter instead of murder. The big thing with any self defense case is knowing when you can act and when you can’t.
They are already building the foundation for a self defense case and Schellinger's past criminal history will play a part in the defense. He was arrested three times.
Per the Philly inquirer:
"Schellenger has a criminal history including arrests in Chester County and Florida, including a 2008 arrest in Florida for disorderly conduct, battery and trespassing although charges were later dropped. He was found guilty of disorderly conduct in 2009 in Chester County, and previously charged in Chester County in August 2001 with burglary, resisting arrest, criminal trespassing, and theft, although the verdict in that case was unknown, the Inquirer reported."
I dont condone the use of the knife, but you can see where this is going.