All that matters is whether the arresting officers reasonably believed it was an illegal weapon under the statute cited for the arrest.
I don’t think so. The officers chased him for no reason beyond him watching them. The knife was an after-the-fact excuse. But, regardless, having a knife was no justification for a deadly nickel ride. Arguing about the knife misses the bigger picture that these officers by their actions or in-actions, killed Freddie Gray.