Problem 9-1. The witness has established personal knowledge, and the opinion is a rational one for a witness to draw, and it will be helpful to the jury. Calling tiles "slippery" is a common characterization.

Problem 9-2. I object to Betty's opinion about what she would have done under different circumstances. It is not rationally based on her perception, because she is basing it on facts that did not happen.

Problem 9-3.

(1) The witness had personal knowledge, and this is the kind of opinion lay people draw based on common experience, so it is rational. It is also helpful because there is no other way to communicate "speed" to a jury.

(2) I object to the opinion about speed of an airplane because it falls outside common experience and the opinion would therefore be irrational. [Note that I have asked you to make the harder argument -- in practice, most judges would probably let this evidence in].

(3) I object to the witness testifying to the quality of the oil. It is not rational for a lay witness to distinguish among types of oil by smell.

(4) The witness has personal knowledge, and each item except (e) seems like the types of oridinary opinions lay witnesses draw and use to communicate, so they are both rational and helpful to the jury. I would not even try to save the last one. It is not rational -- you can't tell the size of a person's ego by the way a stranger walks rights after an accident.

Problem 9-4.

(1) I would have objected to the opinion that the wink was directed "at her" as being not rationally based on perception. [This is a close call -- lots of judges would probably let it in].

(2) I'd object to the witness interpreting the meaning of the wink. This is testimony about another person's mental state which violates the personal knowledge rule (FRE 601).

(3) I'd object to the opinion about the identity of the cologne. This is specialized rather than common knowledge, so the prosecutor must lay a "skilled lay witness" foundation that the witness is familiar with this particular fragrance.

Problem 9-5.

It is important that you be specific. I would object to the opinion that the peel had been on the floor for hours. The witness lacks the necessary perception, and it is not rational to conclude how long something had been in a location based on a single observation. I would not object to the sack of bricks comment.

Problem 9-29.

(1) Response: The witness has personal knowledge, and opinions of height and weight are within common experience.

(2) Response: The witness has personal knowledge, and detecting the smell of alcohol is within adult common experience. There is no other way to communicate this observation.

(3) Response: The witness has personal knowledge. Recognizing a look of anger is within common experience and there is no other way to express it. The expression "like he had stepped on a tack" is just a figure of speech and is not an attempt to communicate an observed fact, so the opinion rule does not apply to it.

(4) Response: There is no good response. I'd argue that the witness has personal knowledge, and is merely expressing an opinion of appearance. There is no issue in the case of them being "killers," so it would not be helpful to require more detail.

(5) Response: The witness has personal knowledge, and opinions of speed and approximate age are within common adult experience.

(6) Response: The witness has personal knowledge, and opinions of what burning rubber smells like and being in a hurry are within common experience and impossible to break down into more specific details.