Laravel update function throws exception

I am currently working with laravel and want to update 'Model' with a controller

public function update(Request $request, $id)
{
    $request->validate([
        'criminal' => 'required|string',
        'crimes' => 'required|string',
        'happened_at' => 'required',
        'description' => 'required|string',
        'report' => 'string|nullable',
        'happened_at' => 'required',
        'testifies' => 'string|nullable',
        'officers' => 'string|nullable',
    ]);

    $case               = Cases::find($id);
    $case->criminal     = $request->input('criminal');
    $case->crimes       = $request->input('crimes');
    $case->officers     = $request->input('officers');
    $case->testifies    = $request->input('testifies');
    $case->report       = $request->input('report');
    $case->happened_at  = $request->input('happened_at');
    $case->crime_desc   = $request->input('description');

    $case->save();
    return redirect('cases.index');
}

It does not save the data and throws an exception:Unexpected data found. Unexpected data found. Data missing

Does somebody know why it throws an exception? Thank you in advance

via Chebli Mohamed