attorneys for lesley mcspadden and michael brown sr. , filed the complaint at the st. louis county courthouse on thursday .
lawsuit alleges that officer darren wilson destroyed evidence after he shot their son on the street of the st. louis suburb last august .
civil suit claims brown did have his hands up in surrender when he was killed - a claim strongly disputed during last year 's investigation .
they are seeking $ 75,000 in compensation , as well as unspecified punitive damages .
also called for a court order prohibiting the use of police techniques ` that demean , disregard , or underserve its african-american population '