But the data, which includes information about 1,166 detainees currently serving life sentences on second-degree murder charges, paints a broad picture of the population currently behind bars. More than half of the people serving life sentences for felony murder are over 50 years old, an age at which imprisonment costs double, but rates of recidivism and criminal behavior plummet. Felony murder cases peaked in the early 1990s, across both the commonwealth and Philadelphia, with an average just under 37 statewide cases between 1991 and 1995. The 2021 PLSE audit of people serving sentences for second-degree murder analyzed hundreds of cases where the organization could identify a co-defendant. According to DOC data, roughly 28% of second-degree murder inmates have served at least 35 years of their life sentences, but some people may have consecutive sentences.