Why MemberExpression for child's overridden property show parent's property

Let's assume we have 2 classes

class A{
   public abstract int Prop1 {get; set;}
}

and it's child

class Child : A{
   [CustomAttr(someval)] 
   override public int Prop1 {get; set;}
}

so later in my code I need to get this custom attribute's val.

bool haveCustomAttr(IExpression<Func<Child, int>> property){
    return ((MemberExpression)property.Body).Member.GetCustomAttributes(typeof(CustomAttr)).Any();
}

so when I call this code

haveCustomAttr(c => c.Prop1)

it's return false because ((MemberExpression)property.Body).Member it's for some reason A.Prop1 and not Child.Prop1

it's possible to fix with more advanced construction like this

((MemberExpression)property.Body).Expression.Type.GetMember(((MemberExpression)property.Body).Member
                .Name)[0].GetCustomAttributes(typeof(CustomAttr), false).Any(); 

But it's still not clear for me why it's threat this expression as base class initially if it's clearly say that it's expression from Child class. Could someone explain logic behind this for me?