Binary search segmentation error for structure

I'm writing a code that is supposed to search for a key, in my case a last name, and then using a binary search attempt to find this key in a different file containing information( First name, Last name, birthday etc..). This information is in a structure called StudentRecord, and is sorted alphabetically by last name using a quicksort function. I cant get the binary code function to work properly. I either get " segmentation fault 11" or name not found when it should be found.

void binary_search( struct StudentRecord *records[], int start, int 
finish, char key[20]){
int i;
int mid;


 start=0;
 finish=i-1;
 while(start<=finish)
 {
    mid=(start+finish)/2;
    if (strcmp(key,records[mid]->LastNames)==0)
        {
            printf("key found at the position %d\n",mid+1);
            exit(0);
        }
    else if(strcmp(key,records[mid]->LastNames)>0)
        {
            finish=finish;
            start=mid+1;

            binary_search(records, start,finish,key);

        }
    else if (strcmp(key,records[mid]->LastNames)<0)
        {
            start=start;
            finish=mid-1;

            binary_search(records, start, finish, key);
    }

        }

        printf("name not found\n");
        }