PBS/PBT · Sep 25 · Investigation Day 12 of 18 · Case A STATIC · Period 1-2
Practice case: three clocks, one intersection (not your case)
This worked model uses the practice values printed on both evidence sheets (pages 2 to 3, "a practice case, not ours"). It is not evidence for Case A or Case B. Use its steps, not its numbers, in your worksheet.
Start: Read the practice case, then return to your own-case worksheet.
Claim ceiling: The window is an estimate with stated assumptions, not a fact. It constrains the timeline; it does not convict anyone inside it.
Part 3 of 4 · Worked example
Practice case: three clocks, one intersection (not your case)
This worked model uses the practice values printed on both evidence sheets (pages 2 to 3, "a practice case, not ours"). It is not evidence for Case A or Case B. Use its steps, not its numbers, in your worksheet.
The supplied practice record
A body measured at 10:00 PM reads 33.0 °C in a 20 °C room. Stiffness is present only in the jaw and fingers. The settled blood fades when pressed.
What to notice: the two thermometers. Every cooling estimate needs both numbers, the body's and the room's, and the room's is the one people forget to write down.
Six steps
- Algor, the drop: 37 minus 33.0 = 4.0 °C dropped. Write the unit every time.
- Algor, the two rates: at 1 °C per hour, 4.0 ÷ 1 = 4.0 hours. At 1.5 °C per hour, 4.0 ÷ 1.5 = about 2.7 hours. Window: 2.7 to 4.0 hours before 10:00 PM, which is about 6:00 PM to 7:20 PM. Assumption: the person started at 37 °C and the room stayed at 20 °C.
- Rigor: stiffness in small muscles only means the clock is in its first few hours. Window: under about 4 hours, so after about 6:00 PM. Assumption: normal temperature and no hard exertion before death.
- Livor: blood settled but fades when pressed means not fixed, so under several hours, call it under 8. Window: after about 2:00 PM. Assumption: a light skin tone and no pressure points hiding the pattern. Position check: the settled blood is on the surfaces that were lowest in the found position, so nothing says moved.
- Intersect: time inside every window. Algor says 6:00 to 7:20 PM, rigor says after 6:00 PM, livor says after 2:00 PM. Overlap: about 6:00 to 7:20 PM. Algor set both ends; the other two agreed and did not narrow it.
- Least-trusted clock and why: livor, because "fades when pressed" is a soft yes-or-no read with a wide schedule. Then the conversion: 33.0 × 1.8 = 59.4, plus 32 = 91.4 °F.
Finished practice product
Practice window: death about 6:00 to 7:20 PM (2.7 to 4.0 hours before the 10:00 PM reading), with the 37 °C start as the load-bearing assumption; rigor and livor agree without narrowing it, and 33.0 °C is 91.4 °F.
What may differ in your case
Your case's clocks may not all give two ends. A body that has reached room temperature gives "at least" and no upper limit. A fixed livor gives a floor. A fully passed rigor gives a floor with a wide schedule behind it. Write the assumption anyway, and let the intersection be a floor if that is all the clocks allow. The practice case had no door log; yours does, in the final part of the period.
The model and these checks do not require another upload. Complete Parts A to E and your door-log timeline check in the one time-of-death worksheet.
Body temperature + room temperature + time of the reading
Stiffness observation + settling observation + the position note your record gives
Algor: (37 minus body) divided by 1 and by 1.5, hours before the reading
Rigor: where the stiffness is, read backward on the schedule
Livor: fixed or not fixed, then the position check
Write the assumption beside each window. Units every time.
Time inside every window is possible.
Time outside any one window is ruled out by that clock.
A floor with no ceiling still counts.
An estimate with stated assumptions, not a fact.
It constrains the timeline; it does not convict anyone inside it.
Name the least-trusted clock and the record condition that weakens it.
Copy each row as printed. Flag the open questions. A credential event is not a person's presence.
Exhibit 014; the Sunday 3:00 AM DOOR HELD row stays an open question.
Read the workflow as text
Find your own-case body temperature, room temperature and the time of the reading, then the stiffness observation, the settling observation and the position note your record gives. Use R3 to make one window per clock: for algor, subtract the body temperature from 37 °C and divide by 1 and by 1.5 to get hours before the reading; for rigor, read where the stiffness is against the schedule; for livor, decide fixed or not fixed and check the settled surfaces against the position note your record gives. Write the assumption beside each window with units. Use R4 to intersect: time inside every window is possible, time outside any one window is ruled out, and a floor with no ceiling still counts. State the ceiling: an estimate with stated assumptions that constrains the timeline and convicts no one inside it, and name the least-trusted clock. In the final part of the period, copy your own case's door log exactly, flag the open questions and leave them questions, and note that a credential event is not proof of a person's presence. The finished worksheet does not claim a measurement, an examination, a role for any name, or a cause of death.
Optional restart cue
Find the next unanswered task ID. Use R2 for the clocks, R3 for each window, R4 for the intersection and ceiling, R5 for the practice numbers and R6 for the door log. Do not switch to the other case or create a second product.
Connection to PLTW
Related PLTW reference:
- Activity 1.2.1 Anatomy of an Autopsy
- Activity 1.2.2 Time of Death
This John Hay original worksheet practices reading a rate, stating an assumption and intersecting independent estimates. It connects by title to PLTW Activities 1.2.1 Anatomy of an Autopsy and 1.2.2 Time of Death; it does not certify official activity completion. The complete required explanation is here; background links are support, not extra assignments.
referenced by title only; all materials in this file are John Hay original work. myPLTW student access is down for technical reasons. When it is restored, this day's PLTW anchor is completed online; until then the portal simulation and these printed materials carry the day.
Official PLTW section hub link: not supplied.
Turn in one worksheet
Complete one time-of-death worksheet, Parts A to E plus your case's door-log timeline check. Hand the paper worksheet to Mr. Mendoza before leaving, or submit one PDF to this section's assignment by September 25 at 11:59 PM. Use your period and investigator code. Do not submit twice; keep notebook pages in your notebook.
The practice case, the optional check and the short check do not require another upload. Complete Parts A to E and the door-log timeline check in the one worksheet.
Case A: submit to Wk5 D12 · The Clock in the Body (PLTW 1.2.2)Keep today's worksheet for the next assigned case lesson, the full examination. Its records must be supplied before you use them; do not assume a cause or manner of death already exists.
What this worksheet cannot claim
The window is an estimate with stated assumptions, not a fact. It constrains the timeline; it does not convict anyone inside it. Nothing today claims that you measured a body, a scene model or a room, examined anything, or established a role, a motive or a cause of death.
The model and these checks do not require another upload. Complete Parts A to E and your door-log timeline check in the one time-of-death worksheet.
No public background reference is printed for this day; the briefing carries the whole required explanation.