Is there anything worse than a slow, muddled, badly lit cop movie? Yes: a slow, muddled, badly lit lady-cop movie. (You get the clichés plus ersatz feminism.) In the insultingly shoddy Impulse, Theresa Russell — she of the ripe smirk and earnest-little-girl doe eyes — plays an underccver vice cop who, for reasons that have absolutely nothing to do with selling the picture, keeps donning rear-zipper miniskirts in order to catch a drug dealer. Russell once seemed a promising actress (she made a fascinating modern temptress in Bad Timing/A Sensual Obsession), but in Impulse she’s set up as both a sexpot victim and an avenging Dirty Harriet. The two pulp poses undercut each other, and Russell ends up looking ridiculous — all because she can’t pout and sneer at the same time.