Why I don't trust church investigations in abuse situations 

This is why I don't trust church investigations (internal or external) in abuse situations:

1. I have never seen it work. While this doesn't mean it won't work in some situations, once the abuse is systemic and ongoing, an "investigation" tends to be more of an outward PR move than an indication the church is actually interested in changing. 

2. The people who pay for the investigation are usually the people who are responsible for the existence of the problem in the first place. When the power holders are also the enablers and abusers--can we really trust them to choose an investigator who will genuinely be objective and honest? Can we really trust them to choose someone who actually knows what they are doing? 

3. Once abuse is ongoing, the church leadership has essentially already lost the trust of their congregation and community. If they haven't, then something is very wrong and may indicate brainwashing and coercive control. It may indicate a very unhealthy congregation. If this is the case, then an investigation is more likely to make things worse, rather than help. Once the leadership has lost the trust of the congregation, an investigation is a bandaid on a gaping wound. It might momentarily staunch the bleeding, but it won't heal the wound. 

Disclaimer: An investigation after abuse is ongoing is different from a church taking preventative measures. Churches who are actively putting policy and care in place BEFORE the abuse, might have a shot. They MIGHT recognize the likelihood of abuse occurring is high, indicating they are humble enough to admit they need help before people have been devastated, eviscerated, and erased.